Solar cell and solar cell panel including the same

ABSTRACT

A solar cell panel is disclosed. The disclosed solar cell panel includes a semiconductor substrate, a conductive region disposed in or on the semiconductor substrate, an electrode connected to the conductive region, a lead electrically connected to the electrode. The electrode includes finger lines, and a bus bar line extending across the finger lines, and electrically connected to the lead. First and second end edge areas are arranged at opposite ends of the bus bar line disposed adjacent to opposite edges of the semiconductor substrate, respectively. The bus bar line includes electrode portions respectively disposed at the first end second end edge areas. Each electrode portion includes an opening formed through the each electrode portion, and an outermost end disposed at a position flush with corresponding ones of the outermost ones of the finger lines or a position outwards of the corresponding outermost finger lines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Korean PatentApplication No. 10-2015-0061337 filed on Apr. 30, 2015 and Korean PatentApplication No. 10-2015-0129283 filed on Sep. 11, 2015 in the KoreanIntellectual Property Office, the disclosures of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a solar cell and a solarcell panel including the same, and more particularly to solar cellsconnected by leads and a solar cell panel including the same.

2. Description of the Related Art

Recently, as existing energy resources such as petroleum and coal aredepleted, interest in alternative energy sources is increasing. Forexample, a solar cell is highlighted as a next-generation cell capableof converting solar energy into electric energy

A plurality of solar cells as mentioned above is connected in series orin parallel by a plurality of ribbons, and is then packaged through apackaging process, for protection thereof, thereby forming a solar cellpanel. Since such a solar cell panel must perform electricity generationfor a long period of time in various environments, the solar cell panelshould secure long-term reliability. In conventional instances, aplurality of solar cells is connected by ribbons, as mentioned above.

However, when solar cells are connected using ribbons having a greatwidth of about 1.5 mm, shading loss may be generated due to such a greatwidth of the ribbons. For this reason, the number of ribbons used forthe solar cells should be reduced. Furthermore, the ribbons exhibitinferior attachment strength, or the solar cells may exhibit anincreased degree of bending due to the ribbons. In such a case, there isa limitation in enhancing the output power of the solar cell panel. Inaddition, the ribbons may be detached from the solar cells, or the solarcells may be damaged. As a result, the solar cell panel may exhibitdecreased reliability.

Although an improvement in electrode structure may be proposed toeliminate the above-mentioned problems, the resultant solar cells mayexhibit degraded efficiency in this instance and, as such, the outputpower of the resultant solar cell panel may be degraded.

SUMMARY OF THE INVENTION

Therefore, the embodiments of the present invention have been made inview of the above problems, and it is an object of the embodiments ofthe present invention to provide a solar cell capable of enhancing theoutput power and reliability of a solar cell panel, and a solar cellpanel including the same.

In accordance with an aspect of the present invention, the above andother objects can be accomplished by the provision of a solar cell panelincluding a solar cell including a semiconductor substrate, a conductiveregion formed in or on the semiconductor substrate, and an electrodeconnected to the conductive region, and at least one lead electricallyconnected to the electrode, to connect the solar cell to another solarcell or an external circuit, wherein the electrode includes a pluralityof finger lines formed to extend in parallel in a first direction andincluding outermost finger lines of the plurality of finger lines thatare respectively disposed adjacent to opposite edges of thesemiconductor substrate, and including a bus bar line formed to extendin a second direction crossing the first direction, and electricallyconnected to the at least one lead, wherein a first end edge area isarranged at one end of the bus bar line disposed adjacent to one edge ofthe opposite edges of the semiconductor substrate, and a second end edgearea is arranged at the other end of the bus bar line disposed adjacentto the other edge of the opposite edges of the semiconductor substrate,wherein the bus bar line includes electrode portions respectivelydisposed at the first and second end edge areas, and each electrodeportion of the electrode portions includes an opening formed through anelectrode portion, and an outermost end disposed at a position flushwith corresponding ones of the outermost finger lines or a positionoutwards of the corresponding outermost finger lines.

In accordance with another aspect of the present invention, there isprovided a solar cell including a semiconductor substrate, a conductiveregion formed in or on the semiconductor substrate, and an electrodeconnected to the conductive region, wherein the electrode includes aplurality of finger lines formed to extend in parallel in a firstdirection while including outermost finger lines disposed adjacent toopposite edges of the semiconductor substrate, and a bus bar line formedto extend in a second direction crossing the first direction, andelectrically connected to a lead to connect the solar cell to anothersolar cell or an external circuit, wherein a first end edge area isarranged at one end of the bus bar line disposed adjacent to one edge ofthe semiconductor substrate, and a second end edge area is arranged atthe other end of the bus bar line disposed adjacent to the other edge ofthe semiconductor substrate, and wherein the bus bar line includeselectrode portions respectively disposed at the first end second endedge areas, and each of the electrode portions includes an openingformed through the electrode portion, and an outermost end disposed at aposition flush with corresponding ones of the outermost finger lines ora position outwards of the corresponding outermost finger lines.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of theembodiments of the present invention will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view illustrating a solar cell panel accordingto an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 ;

FIG. 3 is a sectional view illustrating an example of the solar cellincluded in the solar cell panel of FIG. 1 ;

FIG. 4 is a sectional view illustrating another example of the solarcell included in the solar cell panel of FIG. 1 ;

FIG. 5 is a perspective view briefly illustrating a first solar cell anda second solar cell, which are connected by leads, in the solar cellpanel of FIG. 1 ;

FIG. 6 illustrates one lead before attachment thereof to electrodes ofone solar cell illustrated in FIG. 1 , through a perspective view and asectional view;

FIG. 7 is a sectional view illustrating the lead attached to padsections of the electrode in the solar cell illustrated in FIG. 1 ;

FIG. 8 is a brief sectional view along a VIII-VIII line of FIG. 5 ;

FIG. 9 is a plan view illustrating one solar cell included in the solarcell panel of FIG. 1 and ribbons connected thereto;

FIG. 10 is a photograph of cross-sections of solar cells, to which leadshaving different widths are attached, respectively;

FIG. 11 is a graph depicting measured results of attachment force of thelead to an end of the electrode while varying the width of the lead andan edge distance;

FIG. 12 is a diagram depicting outputs of the solar cell panel measuredwhile varying the width of each lead and the number of leads;

FIG. 13 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention;

FIG. 14 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention;

FIG. 15 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention;

FIG. 16 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention;

FIG. 17 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention;

FIG. 18 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention;

FIG. 19 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention; and

FIG. 20 is a graph depicting measured results of attachment forcemeasured while pulling a lead attached to a solar cell panel using anexperimental device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the example embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The present invention may, however, be embodied in manyalternate forms and should not be construed as limited to theembodiments set forth herein.

In the drawings, illustration of parts having no concern with theembodiments of the present invention is omitted for clarity andsimplicity of description. The same reference numerals designate thesame or very similar elements throughout the specification. In thedrawings, the thicknesses, widths or the like of elements areexaggerated or reduced for clarity of description, and should not beconstrued as limited to those illustrated in the drawings.

It will be understood that the terms “comprises” and/or “comprising,” or“includes” and/or “including” when used in the specification, specifythe presence of stated matters, but do not preclude the presence oraddition of one or more other matters. In addition, it will beunderstood that, when an element such as a layer, film, region, or plateis referred to as being “on” another element, it can be directlydisposed on another element or can be disposed such that an interveningelement is also present therebetween. Accordingly, when an element suchas a layer, film, region, or plate is disposed “directly on” anotherelement, this means that there is no intervening element between the twoelements.

Hereinafter, solar cells and solar cell panels including the sameaccording to embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a perspective view illustrating a solar cell panel accordingto an embodiment of the present invention. FIG. 2 is a cross-sectionalview taken along line II-II in FIG. 1 .

Referring to FIGS. 1 and 2 , the solar cell panel according to theillustrated embodiment, which is designated by reference numeral “100”,includes a plurality of solar cells 150, and leads (or interconnectors)142 for electrically connecting the solar cells 150. The solar cellpanel 100 also includes a sealant 130 for enclosing and sealing thesolar cells 150 and leads 142, a front substrate 110 disposed at a frontside of the solar cells 150 over the sealant 130, and a back substrate200 disposed at a backside of the solar cells 150 over the sealant 130.This will be described in more detail.

First, each solar cell 150 may include a photoelectric converter forconverting solar energy into electric energy, and an electrodeelectrically connected to the photoelectric converter, to collectcurrent, for transfer of the collected current. The solar cells 150 maybe electrically connected in series, in parallel, or in series-parallelby the leads 142. In detail, longitudinally neighboring ones of thesolar cells 150 are electrically connected by corresponding ones of theleads 142 and, as such, the solar cells 150 form strings extending inthe longitudinal direction.

Bus ribbons 145 connect opposite ends of the solar cell strings, indetail, ends of the leads 142 thereof, in an alternating manner. The busribbons 145 may be arranged at opposite ends of the solar cell strings,to extend in a direction crossing the solar cell strings. The busribbons 145 may connect adjacent ones of the solar cell strings, orconnect the solar cell strings to a junction box for preventing backwardflow of current. The material, shape, and connecting structure of thebus ribbons 145 may be diverse and, as such, the embodiment of thepresent invention is not limited thereto.

The sealant 130 may include a first sealant 131 disposed at the frontside of the solar cells 150, and a second sealant 132 disposed at thebackside of the solar cells 150. The first sealant 131 and secondsealant 132 block permeation of moisture or oxygen, which may adverselyaffect the solar cells 150, and enable chemical coupling of componentsof the solar cell panel 100. The solar cell panel 100 may have anintegrated structure. This may be achieved by arranging the backsubstrate 200, second sealant 132, solar cells 150, first sealant 131and front substrate 110 in this order, and then applying heat and/orpressure or the like to the resultant structure through a laminationprocess.

As the first sealant 131 and second sealant 132, ethylene vinyl acetate(EVA) copolymer resin, polyvinyl butyral, silicon resin, ester-basedresin, olefin-based resin, or the like may be used. Of course, theembodiment of the present invention is not limited to such materials.Accordingly, the first and second sealants 131 and 132 may be formed,using various other materials, in accordance with a method other thanlamination. In this instance, the first and second sealants 131 and 132have optical transparency, to allow light incident through the backsubstrate 200 or light reflected from the back substrate 200 to reachthe solar cells 150.

The front substrate 110 is disposed on the first sealant 131 and, assuch, constitutes a front surface of the solar cell panel 100. The frontsubstrate 110 may be made of a material having a strength capable ofprotecting the solar cells 150 from external impact or the like andoptical transparency capable of allowing transmission of light such assunlight. For example, the front substrate 110 may be constituted by aglass substrate or the like. In this instance, the front substrate 110may be constituted by a reinforced glass substrate, for strengthenhancement. In addition, various variations may be applied to the frontsubstrate 110. For example, the front substrate 110 may additionallycontain various materials capable of improving various characteristics.Alternatively, the front substrate 110 may be a sheet or film made ofresin or the like. That is, the embodiment of the present invention isnot limited as to the material of the front substrate 110, and the frontsubstrate 110 may be made of various materials.

The back substrate 200 is a layer disposed on the second sealant 132, toprotect the solar cells 150 at the backside thereof. The back substrate200 may have waterproof, insulation, and ultraviolet blocking functions.

The back substrate 200 may have a strength capable of protecting thesolar cells 150 from external impact or the like. The back substrate 200may also have characteristics allowing transmission of light orreflection of light in accordance with a desired structure of the solarcell panel 150. For example, in a structure of the solar cell panel 150,in which light is incident through the back substrate 200, the backsubstrate 200 may be made of a transparent material. On the other hand,in a structure of the solar cell panel 150, in which light is reflectedby the back substrate 200, the back substrate 200 may be made of anopaque material, a reflective material, or the like. For example, theback substrate 200 may have a substrate structure made of glass.Alternatively, the back substrate 200 may have a film or sheet structureor the like. For example, the back substrate 200 may be ofTedlar/PET/Tedlar (TPT) type or may have a structure in whichpolyvinylidene fluoride (PVDF) resin or the like is formed over at leastone surface of polyethylene terephthalate (PET). PVDF, which is apolymer having a structure of (CH₂CF₂)n, has a double fluorine molecularstructure and, as such, has excellent mechanical properties, weatherresistance and ultraviolet resistance. However, the embodiment of thepresent invention is not limited to the material of the back substrate200.

Hereinafter, an example of one solar cell included in the solar cellpanel according to the illustrated embodiment of the present inventionwill be described in more detail with reference to FIG. 3 .

FIG. 3 is a sectional view illustrating an example of the solar cellincluded in the solar cell panel of FIG. 1 .

Referring to FIG. 3 , the solar cell 150 according to the illustratedembodiment includes a semiconductor substrate 160 including a baseregion 10, conductive regions 20 and 30 formed in the semiconductorsubstrate 160 or on the semiconductor substrate 160, and electrodes 42and 44 respectively connected to the conductive regions 20 and 30. Inthis instance, the conductive regions 20 and 30 may include afirst-conduction-type conductive region 20 having a first conductivityand a second-conduction-type conductive region 30 having a secondconductivity. The electrodes 42 and 44 may include a first electrode 42connected to the first-conduction-type conductive region 20 and a secondelectrode 44 connected to the second-conduction-type conductive region30. The solar cell 150 may further include a first passivation film 22,an anti-reflective film 24, a second passivation film 32, etc.

The semiconductor substrate 160 may be made of crystallinesemiconductor. For example, the semiconductor substrate 160 may be madeof a single-crystalline or polycrystalline semiconductor (for example, asingle-crystalline or polycrystalline silicon). For example, thesemiconductor substrate 160 may be made of a single-crystallinesemiconductor (for example, a single-crystalline semiconductor wafer,for example, a single-crystalline silicon wafer). When the semiconductorsubstrate 160 is made of a single-crystalline semiconductor (forexample, a single-crystalline silicon), the solar cell 150 exhibitsreduced defects because the solar cell 150 is based on the semiconductorsubstrate 160, which has high crystallinity. Thus, the solar cell 150may have excellent electrical characteristics.

The front and/or back surface of the semiconductor substrate 160 mayhave an uneven surface structure having protrusions and grooves throughtexturing. For example, the protrusions and grooves have a pyramid shapehaving an outer surface constituted by a (111)-oriented surface of thesemiconductor substrate 160 while having an irregular size. For example,when the front surface of the semiconductor substrate 160 has increasedsurface roughness in accordance with formation of protrusions andgrooves through texturing, it may be possible to reduce reflectance oflight incident through the front surface of the semiconductor substrate160. Accordingly, an amount of light reaching a pn junction formed bythe base region 10 and first-conduction-type conductive region 20 may beincreased and, as such, shading loss may be minimized. However, theembodiment of the present invention is not limited to theabove-described structure. The semiconductor substrate 160 may not have,at the front and back surfaces thereof, protrusions and grooves formedthrough texturing.

The base region 10 of the semiconductor substrate 160 may be doped witha second-conduction-type dopant at a relatively low doping concentrationand, as such, has the second conductivity. For example, the base region10 may be arranged farther from the front surface of the semiconductorsubstrate 160 or closer to the back surface of the semiconductorsubstrate 160 than the first-conduction-type conductive region 20. Inaddition, the base region 10 may be arranged closer to the front surfaceof the semiconductor substrate 160 or farther from the back surface ofthe semiconductor substrate 160 than the second-conduction-typeconductive region 30. Of course, the embodiment of the present inventionis not limited to such an arrangement, and the location of the baseregion 10 may be varied.

In this instance, the base region 10 may be made of a crystallinesemiconductor containing a second-conduction-type dopant, for example, asingle-crystalline or polycrystalline semiconductor (for example, asingle-crystalline or polycrystalline silicon) containing asecond-conduction-type dopant. For example, the base region 10 may bemade of a single-crystalline semiconductor (for example, asingle-crystalline semiconductor wafer, for example, asingle-crystalline silicon wafer) containing a second-conduction-typedopant.

The second conduction type may be an n-type or a p-type. When the baseregion 10 has n-type conductivity, the base region 10 may be made of asingle-crystalline or polycrystalline semiconductor doped with a Group-Velement such as phosphorous (P), arsenic (As), bismuth (Bi) or antimony(Sb). On the other hand, when the base region 10 has p-typeconductivity, the base region 10 may be made of a single-crystalline orpolycrystalline semiconductor doped with a Group-III element such asboron (B), aluminum (Al), gallium (Ga), or indium (In).

Of course, the embodiment of the present invention is not limited to theabove-described materials, and the base region 10 andsecond-conduction-type dopant may be constituted by various materials.

For example, the base region 10 may have n-type conductivity. Then, thefirst-conduction-type conductive region 20, which forms a pn junctiontogether with the base region 10, has p-type conductivity. When light isirradiated to such a pn junction, electrons produced in accordance witha photoelectric effect migrate toward the back surface of thesemiconductor substrate 160 and, as such, are collected by the secondelectrode 44. Meanwhile, holes migrate toward the front surface of thesemiconductor substrate 160 and, as such, are collected by the firstelectrode 42. As a result, electric energy is generated. Then, holeshaving a lower movement rate than electrons migrate toward the frontsurface of the semiconductor substrate 160, rather than the back surfaceof the semiconductor substrate 160 and, as such, photoelectricconversion efficiency may be enhanced. Of course, the embodiment of thepresent invention is not limited to the above-described conditions, andthe base region 10 and second-conduction-type conductive region 30 mayhave p-type conductivity, and the first-conduction-type conductiveregion 20 may have n-type conductivity.

The first-conduction-type conductive region 20, which has the firstconductivity opposite that of the base region 10, may be formed at thefront surface side of the semiconductor substrate 160. Thefirst-conduction-type conductive region 20 forms a pn junction togetherwith the base region 10 and, as such, constitutes an emitter region toproduce carriers in accordance with a photoelectric effect.

In the illustrated embodiment, the first-conduction-type conductiveregion 20 may be constituted by a doped region constituting a portion ofthe semiconductor substrate 160. In this instance, thefirst-conduction-type conductive region 20 may be made of a crystallinesemiconductor containing a first-conduction-type dopant. For example,the first-conduction-type conductive region 20 may be made of asingle-crystalline or polycrystalline semiconductor (for example, asingle-crystalline or polycrystalline silicon) containing afirst-conduction-type dopant. For example, the first-conduction-typeconductive region 20 may be made of single-crystalline semiconductor(for example, a single-crystalline semiconductor wafer, for example, asingle-crystalline silicon wafer) containing a first-conduction-typedopant. When the first-conduction-type conductive region 20 constitutesa portion of the semiconductor substrate 160, as described above,junction characteristics of the base region 10 and first-conduction-typeconductive region 20 may be enhanced.

Of course, the embodiment of the present invention is not limited to theabove-described conditions and, the first-conduction-type conductiveregion 20 may be formed on the semiconductor substrate 160, separatelyfrom the semiconductor substrate 160. In this instance, thefirst-conduction-type conductive region 20 may be constituted by asemiconductor layer having a crystalline structure different from thatof the semiconductor substrate 160, for easy formation thereof on thesemiconductor substrate 160. For example, the first-conduction-typeconductive region 20 may be formed by doping an amorphous semiconductor,microcrystalline semiconductor, or polycrystalline semiconductor (forexample, an amorphous silicon, microcrystalline silicon, orpolycrystalline silicon), which may be easily manufactured throughvarious methods such as deposition, with a first-conduction-type dopant.Of course, other variations are possible.

The first-conduction-type may be p-type or n-type. When thefirst-conduction-type conductive region 20 has p-type conductivity, thefirst-conduction-type conductive region 20 may be made of asingle-crystalline or polycrystalline semiconductor doped with aGroup-III element such as boron (B), aluminum (Al), gallium (Ga), orindium (In). On the other hand, when the first conduction typeconductive region has n-type conductivity, the first-conduction-typeconductive region 20 may be made of a single-crystalline orpolycrystalline semiconductor doped with a Group-V element such asphosphorous (P), arsenic (As), bismuth (Bi) or antimony (Sb). Forexample, the first-conduction-type conductive region 20 may be asingle-crystalline or polycrystalline semiconductor doped with boron. Ofcourse, the embodiment of the present invention is not limited to theabove-described materials, and various materials may be used as thefirst-conduction-type dopant.

In the drawings, the first-conduction-type conductive region 20 isillustrated as having a homogeneous structure having a uniform dopingconcentration throughout the first-conduction-type conductive region 20.Of course, the embodiment of the present invention is not limited to theabove-described structure. In another embodiment, thefirst-conduction-type conductive region 20 may have a selectivestructure, as illustrated in FIG. 4 .

Referring to FIG. 4 , the first-conduction-type conductive region 20,which has a selective structure, may include a first portion 20 a formedadjacent to the first electrode 42, to contact the first electrode 42,and a second portion 20 b formed at the remaining portion of thefirst-conduction-type conductive region 20, for example, a portion ofthe first-conduction-type conductive region 20, except for the firstportion 20 a.

The first portion 20 a may have a high doping concentration and, assuch, may have relatively low resistance. The second portion 20 b mayhave a lower doping concentration than the first portion 20 a and, assuch, may have relatively high resistance. The first portion 20 a mayhave a greater thickness than the second portion 20 b. That is, thejunction depth of the first portion 20 a may be greater than that of thesecond portion 20 b.

Thus, in the illustrated embodiment, a shallow emitter is realized byforming the second portion 20 b having relatively high resistance at aportion of the first-conduction-type conductive region 20, except forthe first portion 20 a corresponding to the first electrode 42, uponwhich light is incident. Accordingly, the current density of the solarcell 150 may be enhanced. In addition, it may be possible to reducecontact resistance of the first-conduction-type conductive region 20 tothe first electrode 42 by forming the first portion 20 a having arelatively low resistance at a portion of the first-conduction-typeconductive region 20 adjacent to the first electrode 42. Accordingly,maximal efficiency may be achieved.

The first-conduction-type conductive region 20 may have variousstructures and various shapes other than the above-described structuresand shapes.

Again referring to FIG. 3 , the second-conduction-type conductive region30, which has the second conductivity identical to that of the baseregion 10 while having a higher doping concentration than the baseregion 10, may be formed at the back surface side of the semiconductorsubstrate 160. The second-conduction-type conductive region 30 forms aback surface field region, which generates a back surface field, toprevent loss of carriers caused by re-coupling (or recombination)thereof at a surface of the semiconductor substrate 160 (for example,the back surface of the semiconductor substrate 160).

In the illustrated embodiment, the second-conduction-type conductiveregion 30 may be constituted by a doped region constituting a portion ofthe semiconductor substrate 160. In this instance, thesecond-conduction-type conductive region 30 may be made of a crystallinesemiconductor containing a second-conduction-type dopant. For example,the second-conduction-type conductive region 30 may be made of asingle-crystalline or polycrystalline semiconductor (for example, asingle-crystalline or polycrystalline silicon) containing asecond-conduction-type dopant. For example, the second-conduction-typeconductive region 30 may be made of single-crystalline semiconductor(for example, a single-crystalline semiconductor wafer, for example, asingle-crystalline silicon wafer) containing a second-conduction-typedopant. When the second-conduction-type conductive region 30 constitutesa portion of the semiconductor substrate 160, as described above,junction characteristics of the base region 10 andsecond-conduction-type conductive region 30 may be enhanced.

Of course, the embodiment of the present invention is not limited to theabove-described conditions and, the second-conduction-type conductiveregion 30 may be formed on the semiconductor substrate 160, separatelyfrom the semiconductor substrate 160. In this instance, thesecond-conduction-type conductive region 30 may be constituted by asemiconductor layer having a crystalline structure different from thatof the semiconductor substrate 160, for easy formation thereof on thesemiconductor substrate 160. For example, the second-conduction-typeconductive region 30 may be formed by doping an amorphous semiconductor,microcrystalline semiconductor, or polycrystalline semiconductor (forexample, an amorphous silicon, microcrystalline silicon, orpolycrystalline silicon), which may be easily manufactured throughvarious methods such as deposition, with a second-conduction-typedopant. Of course, other variations are possible.

The second-conduction-type may be an n-type or a p-type. When thesecond-conduction-type conductive region 30 has n-type conductivity, thesecond-conduction-type conductive region 30 may be made of asingle-crystalline or polycrystalline semiconductor doped with a Group-Velement such as phosphorous (P), arsenic (As), bismuth (Bi) or antimony(Sb). On the other hand, the second conduction type has p-typeconductivity, the second-conduction-type conductive region 30 may bemade of a single-crystalline or polycrystalline semiconductor doped witha Group-III element such as boron (B), aluminum (Al), gallium (Ga), orindium (In). For example, the second-conduction-type conductive region30 may be a single-crystalline or polycrystalline semiconductor dopedwith phosphorous. Of course, the embodiment of the present invention isnot limited to the above-described materials, and various materials maybe used as the second-conduction-type dopant. In addition, thesecond-conduction-type dopant of the second-conduction-type conductiveregion 30 may be identical to the second-conduction-type dopant of thebase region 10 or may differ from the second-conduction-type dopant ofthe base region 10.

In this embodiment, the second-conduction-type conductive region 30 isillustrated as having a homogeneous structure having a uniform dopingconcentration throughout the second-conduction-type conductive region30. Of course, the embodiment of the present invention is not limited tothe above-described structure. In another embodiment, thesecond-conduction-type conductive region 30 may have a selectivestructure. In the selective structure, the second-conduction-typeconductive region 30 may have a high doping concentration, a greatjunction depth, and low resistance at a portion thereof adjacent to thesecond electrode 44 while having a low doping concentration, a smalljunction depth, and high resistance at the remaining portion of thesecond-conduction-type conductive region 30. The selective structure ofthe second-conduction-type conductive region 30 is identical or similarto that of the first-conduction-type conductive region 20 illustrated inFIG. 4 and, as such, the description given of the first-conduction-typeconductive region 20 with reference to FIG. 4 in association with theselective structure may be applied to the second-conduction-typeconductive region 30. In another embodiment, the second-conduction-typeconductive region 30 may have a local structure, as illustrated in FIG.4 .

Referring to FIG. 4 , the second-conduction-type conductive region 30,which has a local structure, may include a first portion 30 a locallyformed at a portion of the second-conduction-type conductive region 30connected to the second electrode 44. Accordingly, thesecond-conduction-type conductive region 30 exhibits reduced contactresistance to the second electrode 44 at the portion thereof connectedto the second electrode 44 and, as such, may have excellent fill factor(FF) characteristics. On the other hand, no second-conduction-typeconductive region 30 constituted by a doped region is formed at a regionnot connected to the second electrode 44 and, as such, re-coupling (orrecombination) possibly occurring at the doped region may be reduced.Accordingly, short-circuit current density Jsc and open-circuit voltagemay be enhanced. In addition, excellent internal quantum efficiency(IQE) may be exhibited at the region where no second-conduction-typeconductive region is formed and, as such, characteristics associatedwith a long-wavelength light may be excellent. Accordingly, it may bepossible to greatly enhance characteristics associated with along-wavelength light, as compared to the homogenous structure andselective structure having a doped region throughout the structure.Thus, the second-conduction-type conductive region 30, which has thelocal structure as described above, may be excellent in terms of fillfactor, short-circuit current density, and open-circuit voltage and, assuch, may achieve an enhancement in efficiency of the solar cell 150.

The second-conduction-type conductive region 30 may have variousstructures other than the above-described structures.

Again referring to FIG. 3 , the first passivation film 22 andanti-reflective film 24 are sequentially formed over the front surfaceof the semiconductor substrate 160, for example, on thefirst-conduction-type conductive region 20 formed in or on thesemiconductor substrate 160. The first electrode 42 is electricallyconnected to (for example, contacts) the first-conduction-typeconductive region 20 through the first passivation film 22 andanti-reflective film 24 (for example, through openings 102).

The first passivation film 22 and anti-reflective film 24 may besubstantially formed throughout the front surface of the semiconductorsubstrate 160, except for the openings 102 corresponding to the firstelectrode 42.

The first passivation film 22 is formed to contact thefirst-conduction-type conductive region 20 and, as such, inactivatesdefects present in the surface or bulk of the first-conduction-typeconductive region 20. Thus, recombination sites of minority carriers areremoved and, as such, open-circuit voltage Voc of the solar cell 150 maybe increased. The anti-reflective film 24 reduces reflectance of lightincident upon the front surface of the semiconductor substrate 160.Thus, the amount of light reaching a pn junction formed by the baseregion 10 and the first-conduction-type conductive region 20 may beincreased in accordance with reduced reflectance of light incident uponthe front surface of the semiconductor substrate 160. Accordingly,short-circuit current Isc of the solar cell 150 may be increased. As aresult, the open-circuit voltage and short-circuit current Isc of thesolar cell 150 may be increased by the first passivation film 22 andanti-reflective film 24 and, as such, the efficiency of the solar cell150 may be enhanced.

The first passivation film 22 may be made of various materials. Forexample, the first passivation film 22 may have a single-layer structureincluding one film selected from the group consisting of a siliconnitride film, a hydrogen-containing silicon nitride film, a siliconoxide film, a silicon oxynitride film, an aluminum oxide film, an MgF₂film, a ZnS film, a TiO₂ film, and a CeO₂ film or may have a multilayerstructure including two or more of the above-listed films incombination. For example, when the first-conduction-type conductiveregion 20 has n-type conductivity, the first passivation film 22 mayinclude a silicon oxide film or silicon nitride film having fixedpositive charges. On the other hand, when the first-conduction-typeconductive region 20 has p-type conductivity, the first passivation film22 may include an aluminum oxide film having fixed negative charges.

The anti-reflective film 24 may be made of various materials. Forexample, the anti-reflective film 24 may have a single-layer structureincluding one film selected from the group consisting of a siliconnitride film, a hydrogen-containing silicon nitride film, a siliconoxide film, a silicon oxynitride film, an aluminum oxide film, an MgF₂film, a ZnS film, a TiO₂ film, and a CeO₂ film or may have a multilayerstructure including two or more of the above-listed films incombination. For example, the anti-reflective film 24 may include asilicon oxide film.

Of course, the embodiment of the present invention is not limited to theabove-described materials, and the first passivation film 22 andanti-reflective film 24 may be made of various materials. One of thefirst passivation film 22 and anti-reflective film 24 may perform boththe anti-reflection function and the passivation function and, as such,the other of the first passivation film 22 and anti-reflective film 24may be omitted. Various films other than the first passivation film 22and anti-reflective film 24 may also be formed on the semiconductorsubstrate 160. In addition, various variations are possible.

The first electrode 42 is electrically connected to thefirst-conduction-type conductive region 20 via the openings 102 formedthrough the first passivation film 22 and anti-reflective film 24 (thatis, through the first passivation film 22 and anti-reflective film 24).The first electrode 42 may be made of a material having excellentelectrical conductivity (for example, metal). The first electrode 42 mayhave a certain pattern to allow transmission of light. A detailedstructure of the first electrode 42 will be described later withreference to FIG. 9 .

The second passivation film 32 is formed on the back surface of thesemiconductor substrate 160, for example, on the second-conduction-typeconductive region 30 formed at the semiconductor substrate 160. Thesecond electrode 44 is electrically connected to (for example, contacts)the second-conduction-type conductive region 30 through the secondpassivation film 32 (for example, through openings 104).

The second passivation film 32 may be substantially formed throughoutthe back surface of the semiconductor substrate 160, except for theopenings 104 corresponding to the second electrode 44.

The second passivation film 32 is formed to contact thesecond-conduction-type conductive region 30 and, as such, inactivatesdefects present in the surface or bulk of the second-conduction-typeconductive region 30. Thus, recombination sites of minority carriers areremoved and, as such, open-circuit voltage Voc of the solar cell 150 maybe increased.

The second passivation film 32 may be made of various materials. Forexample, the second passivation film 32 may have a single-layerstructure including one film selected from the group consisting of asilicon nitride film, a hydrogen-containing silicon nitride film, asilicon oxide film, a silicon oxynitride film, an aluminum oxide film,an MgF₂ film, a ZnS film, a TiO₂ film, and a CeO₂ film or may have amultilayer structure including two or more of the above-listed films incombination. For example, when the second-conduction-type conductiveregion 30 has n-type conductivity, the second passivation film 32 mayinclude a silicon oxide film or silicon nitride film having fixedpositive charges. On the other hand, when the second-conduction-typeconductive region 30 has p-type conductivity, the second passivationfilm 32 may include an aluminum oxide film having fixed negativecharges.

Of course, the embodiment of the present invention is not limited to theabove-described materials, and the second passivation film 32 may bemade of various materials. Various films other than the secondpassivation film 32 may also be formed on the back surface of thesemiconductor substrate 160. In addition, various variations arepossible.

The second electrode 44 is electrically connected to thesecond-conduction-type conductive region 30 via the openings 104 formedthrough the second passivation film 32. The second electrode 44 may bemade of a material having excellent electrical conductivity (forexample, metal). The second electrode 44 may have a certain pattern toallow transmission of light. A detailed structure of the secondelectrode 44 will be described later.

As described above, in this embodiment, the first and second electrodes42 and 44 of the solar cell 150 have predetermined patterns and, assuch, the solar cell 150 has a bi-facial structure in which light can beincident upon both the front and back surfaces of the semiconductorsubstrate 160. Accordingly, the amount of light utilized by the solarcell 150 is increased and, as such, an enhancement in efficiency of thesolar cell 150 may be achieved.

Of course, the embodiment of the present invention is not limited to theabove-described structure. The second electrode 44 may have a structureformed throughout the back surface of the semiconductor substrate 160.The first and second-conduction-type conductive regions 20 and 30 andthe first and second electrodes 42 and 44 may also be arranged at onesurface of the semiconductor substrate 160 (for example, the backsurface). In addition, at least one of the first andsecond-conduction-type conductive regions 20 and 30 may be formed toextend over both surfaces of the semiconductor substrate 160. That is,the above-described solar cell 150 is only illustrative and, as such,the embodiment of the present invention is not limited thereto.

The above-described solar cell 150 is electrically connected to another,neighboring solar cell 150 by leads 142. This will be described in moredetail with reference to FIG. 5 together with FIGS. 1 and 2 .

FIG. 5 is a perspective view briefly illustrating a first solar cell 151and a second solar cell 152, which are connected by leads 142, in thesolar cell panel 100 of FIG. 1 . In FIG. 5 , each solar cell 150 isbriefly illustrated mainly in conjunction with the semiconductorsubstrate 160 and electrodes 42 and 44 thereof. FIG. 6 illustrates onelead 142 before attachment thereof to the electrodes 42 and 44 of onesolar cell 150 illustrated in FIG. 1 , through a perspective view and asectional view. FIG. 7 is a sectional view illustrating the lead 142attached to pad sections (designated by reference numeral “422” in FIG.9 ) of the electrode 42 or 44 in the solar cell 150 illustrated in FIG.1 . FIG. 8 is a brief sectional view along a VIII-VIII line of FIG. 5 .In FIG. 7 , only the pad sections 422 and lead 142 are shown forsimplicity of illustration and description. In FIG. 8 , illustration isgiven mainly in conjunction with leads 142 connecting the first solarcell 151 and the second solar cell 152.

As illustrated in FIG. 5 , two neighboring solar cells 150 of aplurality of solar cells 150 (for example, the first solar cell 151 andsecond solar cell 152) may be connected by leads 142. In this instance,the leads 142 connect the first electrode 42 disposed at the frontsurface of the first solar cell 151 and the second electrode 44 disposedat the back surface of the second solar cell 152 arranged at one side ofthe first solar cell 151 (a left lower side of FIG. 5 ). Other leads1420 a connect the second electrode 44 disposed at the back surface ofthe first solar cell 151 and the first electrode 42 disposed at thefront surface of another solar cell to be arranged at the other side ofthe first solar cell 151 (a right upper side of FIG. 5 ). Other leads1420 b connect the first electrode 42 disposed at the front surface ofthe second solar cell 152 and the second electrode 44 disposed at theback surface of another solar cell to be arranged at one side of thesecond solar cell 152 (a left lower side of FIG. 5 ). Thus, a pluralityof solar cells 150 may be connected by the leads 142, 1420 a and 1420 b,to form one solar cell string. In the following description, descriptiongiven of leads 142 may be applied to all leads 142 connecting twoneighboring solar cells 150.

In this embodiment, each lead 142 may include a first section 1421connected to the first electrode 42 of the first solar cell 151 (forexample, a bus bar line 42 b of the first electrode 42) at the frontsurface of the first solar cell 151 while extending from a first edge161 of the first solar cell 151 toward a second edge 162 of the firstsolar cell 151 opposite the first edge 161, a second section 1422connected to the second electrode 44 of the second solar cell 152 (forexample, a bus bar line 44 b of the second electrode 44) at the backsurface of the second solar cell 152 while extending from a first edge161 of the second solar cell 152 towards a second edge 162 of the secondsolar cell 152 opposite the first edge 161 of the second solar cell 152,and a third section 1423 extending from the front surface of the firstsolar cell 151 at the second edge 162 of the first solar cell 151 to theback surface of the second solar cell at the first edge 161 of thesecond solar cell 152, to connect the first section 1421 and secondsection 1422. Accordingly, the lead 142 may be arranged to extend acrossthe first solar cell 151 along a portion of the first solar cell 151while extending across the second solar cell 152 along a portion of thesecond solar cell 152. Since the lead 142 is formed only in regionscorresponding to portions of the first and second solar cells 151 and152 (for example, the bus bar electrodes 42 b) while having a smallerwidth than the first and second solar cells 151 and 152), the lead 142may effectively connect the first and second solar cells 151 and 152 inspite of a small area thereof.

For example, the lead 142 may be arranged at the corresponding first andsecond electrodes 42 and 44 of the first and second solar cells 151 and152, to extend lengthily along the bus bar lines 42 b of the first andsecond electrodes and 44 while contacting the bus bar lines 42 b.Accordingly, the lead 142 continuously contacts the first and secondelectrodes 42 and 44 and, as such, electrical connection characteristicsmay be enhanced. Of course, the embodiment of the present invention isnot limited to the above-described arrangement. The bus bar lines 42 bmay be omitted. In this instance, the leads 142 may be arranged toextend in a direction crossing a plurality of finger lines 42 a, to beconnected to the finger lines 42 a through connection therebetween whileintersecting the finger lines 42 a. Of course, the embodiment of thepresent invention is not limited to such an arrangement.

With reference to one surface of each solar cell 150, a plurality ofleads 142 is provided and, as such, electrical connectioncharacteristics of the solar cell 150 to another, neighboring solar cell150 may be enhanced. For example, in this embodiment, each lead 142 isconstituted by a wire having a smaller width than a ribbon having arelatively great width (for example, 1 to 2 mm), which has been used inconventional instances. To this end, a greater number of leads 142 (forexample, two to five) than that of ribbons as described above are usedwith reference to one surface of each solar cell 150.

As illustrated in FIG. 6 , in this embodiment, each lead 142 includes acore layer 142 a, and a coating layer 142 b coated over an outer surfaceof the core layer 142 a to a small thickness. The core layer 142 a isconstituted by a wire having excellent electrical conductivity or thelike, to substantially transfer current. The coating layer 142 b mayhave various functions for protecting the core layer 142 a or enhancingattachment characteristics of the lead 142. For example, the coatinglayer 142 b may include a solder material and, as such, may function toeasily attach the lead 142 to the electrodes 42 and 44 in accordancewith melting thereof by heat. Thus, the lead 142 may be easily attachedto the electrodes 42 and 44 in accordance with soldering throughapplication of heat after the lead 142 is disposed on the electrodes 42and 44, without using a separate adhesive. Accordingly, a tabbingprocess may be simplified.

In this instance, the tabbing process may be carried out by coating aflux over the lead 142, disposing the flux-coated lead 142 on theelectrodes 42 and 44, and then applying heat to the flux-coated lead142. The flux is adapted to prevent formation of an oxide filmobstructing soldering. In this regard, the flux may not be necessary.

The core layer 142 a may include a material exhibiting excellentelectrical conductivity (for example, metal, for example, Ni, Cu, Ag, orAl) as a major material thereof (for example, a material having acontent of 50 wt % or more, for example, a material having a content of90 wt % or more). When the coating layer 142 b includes a soldermaterial, the coating layer 142 b may include a material such as Pb, Sn,SnIn, SnBi, SnPb, SnPbAg, SnCuAg or SnCu as a major material thereof. Ofcourse, the embodiment of the present invention is not limited to theabove-described materials and, the core layer 142 a and coating layer142 b may include various materials.

In another example, the lead 142 may be attached to the electrodes 42and 44, using a separate conductive adhesive. In this instance, the lead142 may or may not include the coating layer 142 b. The conductiveadhesive may be a material constituted by an epoxy-based synthetic resinor silicon-based synthetic resin containing conductive particles of Ni,Al, Ag, Cu, Pb, Sn, SnIn, SnBi, SnP, SnPbAg, SnCuAg, SnCu or the like.The material is maintained in a liquid phase at normal temperature, andis thermally cured by heat applied thereto. When such a conductiveadhesive is used, it may be possible to attach the lead 142 to theelectrodes 42 and 44 by disposing the conductive adhesive on theelectrodes 42 and 44, disposing the lead 142 on the conductive adhesive,and then applying heat to the lead 142, or coating or disposing theconductive adhesive on the surface of the lead 142, disposing the lead142 on the electrodes 42 and 44, and then applying heat to the lead 142.

When the wire, which has a smaller width than the existing ribbon, isused as the lead 142, material costs may be greatly reduced. Since thelead 142 has a smaller width than the ribbon, it may be possible to usea sufficient number of leads 142 and, as such, the movement distance ofcarriers may be minimized. Accordingly, the output power of the solarcell panel 100 may be enhanced.

The wire constituting the lead 142 in accordance with this embodimentmay have a circular or oval cross-section, a curved cross-section, or around cross-section, to induce reflection or diffuse reflection.Accordingly, light reflected from a round surface of the wireconstituting the lead 142 may be reflected or totally reflected upon thefront substrate 110 or back substrate 200 disposed at the front surfaceor back surface of the solar cell 150 and, as such, may be againincident upon the solar cell 150. Thus, the output power of the solarcell panel 100 may be effectively enhanced. Of course, the embodiment ofthe present invention is not limited to the above-described shape, andthe wire constituting the lead 142 may have a quadrangular shape or apolygonal shape. The wire may also have various other shapes.

In this embodiment, the lead 142 may have a width W1 of 250 to 500 μm.By virtue of the lead 142, which has a wire structure while having theabove-described width, it may be possible to effectively transfercurrent generated in the solar cell 150 to a circuit arranged outsidethe solar cell 150 (for example, a bus ribbon or a bypass diode of ajunction box) or to another solar cell 150. In this embodiment, the lead142 may be fixed to the electrodes 42 and 44 of the solar cell 150 afterbeing independently disposed on the electrodes and 44 under thecondition that the lead 142 is not inserted in to a separate layer orfilm or the like. Accordingly, when the width W1 of the lead 142 is lessthan 250 μm, the strength of the lead 142 may be insufficient. Inaddition, the lead 142 may exhibit inferior electrical connectioncharacteristics and low attachment force because the connection area ofthe lead 142 to the electrodes 42 and 44 is too small. On the otherhand, when the width W1 of the lead 142 is greater than 500 μm, thematerial costs of the lead 142 increase. In addition, the lead 142 mayobstruct incidence of light upon the front surface of the solar cell 150and, as such, shading loss may increase. In addition, force applied tothe lead 142 in a direction away from the electrodes 42 and 44 mayincrease and, as such, an attachment force between the lead 142 and theelectrodes 42 and 44 may be reduced. In severe instances, cracks or thelike may be generated at the electrodes 42 and 44 or the semiconductorsubstrate 160. For example, the width W1 of the lead 142 may be 350 to450 μm (for example, 350 to 400 μm). In this range, it may be possibleto achieve an enhancement in output power while increasing theattachment force to the electrodes 42 and 44.

In this instance, the thickness of the coating layer 142 b in the lead142, for example, T2, is as small as 10% or less the width of the corelayer 142 a before the tabbing process (for example, equal to or lessthan 20 μm, for example, 7 to 20 μm). When the thickness T2 of thecoating layer 142 b is less than 7 μm, it may be impossible to smoothlycarry out the tabbing process. On the other hand when the thickness T2of the coating layer 142 b is greater than 20 μm, material costs mayincrease. Furthermore, the strength of the lead 142 may be reduced dueto a reduction in width of the core layer 142 a. Once the lead 142 isattached to the solar cell 150 in accordance with the tabbing process,the coating layer 142 b flows downwards and, as such, is thicklydeposited between the lead 142 and the solar cell 150 (for example,between the lead 142 and the pad sections 422 of the electrodes 42 and44) while being thinly deposited on a surface of the core layer 142 aopposite the solar cell 150, as illustrated in FIG. 7 . The portion ofthe coating layer 142 b disposed between the lead 142 and the solar cell150 may have a width W7 equal to or greater than the diameter of thecore layer 142 of the lead 142. The coating layer 142 b may have athickness T1 of 11 to 21 μm at a portion thereof between the lead 142and the pad sections 422 of the electrodes 42 and 44. On the other hand,the coating layer 142 b may have a thickness T2 as small as 2 μm or less(for example, 0.5 to 1.5 μm) at the remaining portion thereof. In thespecification, the width W1 of the lead 142 may mean a width or diameterof the core layer 142 a in a plane perpendicular to a thicknessdirection of the solar cell 150 while passing through a center of thelead 142. In this instance, the coating layer 142 b has a very smallthickness at a portion thereof disposed at the center of the core layer142 a and, as such, has little influence on the width of the lead 142.In this regard, the width W1 of the lead 142 may mean a sum of widths orradiuses of the core layer 142 a and coating layer 142 b in the planeperpendicular to the thickness direction of the solar cell 150 whilepassing through the center of the core layer 142 a.

As described above, an enhancement in output power may be achieved bythe provision of the wire-shaped leads 142. In this embodiment, however,neighboring solar cells 150 are electrically connected using leads 142having a smaller width than those of conventional instances and, assuch, the attachment force of the leads 142 to the electrodes 42 and 44may be insufficient because the attachment area of each lead 142 to theelectrodes 42 and 44 may be small. Furthermore, when the leads 142 havea round cross-section having a circular, oval or curved shape, theattachment area of each lead 142 to the electrodes 42 and 44 may befurther reduced and, as such, the attachment force of each lead 142 maybe further reduced. In addition, when the leads 142 have a roundcross-section having a circular, oval or curved shape, the solar cell150 or semiconductor substrate 160 may be more easily bent because thethickness of each lead 142 may be relatively increased.

For example, in a region between the first solar cell 151 and the secondsolar cell 152, each lead 142 should extend from a position over thefront surface of the first solar cell 151 to a position beneath the backsurface of the second solar cell 152. For this reason, the lead 142 maybe bent in this region. That is, as illustrated in FIG. 8 , the firstsection 1421 of the lead 142 is disposed on the first electrode 42 ofthe first solar cell 151 while being maintained in an attached (forexample, contact) state to the first electrode 42, and the secondsection 1422 of the lead 142 is disposed on the second electrode 44 ofthe second solar cell 152 while being maintained in an attached (forexample, contact) state to the second electrode 44. In this instance,the third section 1423 of the lead 142 should be connected between thefirst section 1421 and the second section 1422 while preventing thefirst and second sections 1421 and 1422 from being bent. To this end,the third section 1423 may include a portion 1423 a bent to have an arcshape convex toward the front surface of the first solar cell 151, so asto be spaced apart from the first solar cell 151 by a predetermineddistance at the vicinity of the second edge 162 of the first solar cell151, and a portion 1423 b bent to have an arc shape convex toward theback surface of the second solar cell 152, and connected to the portion1423 a while having an inflection point with reference to the portion1423 a, so as to be spaced apart from the first solar cell 151 by apredetermined distance at the vicinity of the first edge 161 of thesecond solar cell 152.

Each of the bent portions 1423 a and 1423 b of the third section 1423has a part extending from a connection point of the third section 1423connected to a corresponding one of the first and second sections 1421and 1422 (for example, a point corresponding to the corresponding edgeof the first solar cell 151 or second solar cell 152) in a directionaway from a corresponding one of the first and second solar cells 151and 152. As a result, the lead 142 is subjected to force in a directionaway from the electrodes 42 and 44 in regions corresponding to facingedges of the solar cells 150.

As the boundary between the first section 1421 and the third section1423 or the boundary between the second section 1422 and the thirdsection 1423 (for example, a connection point of the lead 142 connectedto the electrode 42 or 44) is closer to the corresponding edge of thecorresponding solar cell 150, the corresponding arc-shaped portion ofthe third section 1423 has a gradually reduced radius of curvature. Inthis instance, force applied to the lead 142 in a direction away fromthe solar cells 150 in regions adjacent to the facing edges of the solarcells 150 is increased and, as such, an attachment force of the lead 142to the electrodes 42 and 44 may be reduced. For this reason, when thewire-shaped leads 142 are provided, as in this embodiment, portions ofthe electrodes 42 and 44 connected to the leads 142 while being arrangedadjacent to the solar cells 150 (for example, pad sections 422, to whichthe leads 142 are attached at a wide area while having high couplingforce) should be spaced apart from the corresponding edges of the solarcells 150 by a predetermined distance or more and, as such, the lead 142may be attached to the electrodes 42 and 44 while having sufficientcoupling force or attachment force.

In this embodiment, accordingly, the electrodes 42 and 44 of the solarcells 150 are designed, taking into consideration the above-describedconditions. This will be described in detail with reference to FIG. 9 .Hereinafter, a detailed description will be given in conjunction withthe first electrode 42 with reference to FIG. 9 , and the secondelectrode 44 is then described.

FIG. 9 is a plan view illustrating one solar cell included in the solarcell panel of FIG. 1 and ribbons connected thereto.

Referring to FIG. 9 , in the illustrated embodiment, the solar cell 150(or the semiconductor substrate 160) may be divided into an electrodearea EA and an edge area PA. In this instance, the solar cell 150 (orthe semiconductor substrate 160) may include, for example, first andsecond edges 161 and 162 parallel to finger lines 42 a, and third andfourth edges 163 and 164 crossing (for example, perpendicularly crossingor inclinedly crossing) the finger lines 42 a. The third and fourthedges 163 and 164 may include respective central portions 163 a and 164a occupying large portions of the third and fourth edges 163 and 164,and respective inclined portions 163 b and 164 b connected to the firstand second edges 161 and 162 while extending inclinedly from respectivecentral portions 163 a and 164 a. Accordingly, the solar cell 150 mayhave, for example, an almost octagonal shape when viewed in a plane. Ofcourse, the embodiment of the present invention is not limited to theabove-described shape, and the planar shape of the solar cell 150 may bevaried.

In this embodiment, the electrode area EA may be an area where thefinger lines 42 a, which extend in parallel, are arranged at a uniformpitch P. The electrode area EA may include a plurality of electrodeareas divided by leads 142. The edge area PA may be an area definedbetween two adjacent ones of the electrode areas while being arrangedadjacent to a corresponding one of the edges of the semiconductorsubstrate 160 or solar cell 150 (for example, edges extending in alongitudinal direction of the leads 142 or bus bar lines 42 b or edgescrossing (perpendicularly crossing) the leads 142 or bus bar lines 42b). In this instance, the edge area PA may be an area where electrodeportions 424 a and 424 b are arranged in a lower density than that ofthe finger lines 42 a in the electrode area EA or an area where noelectrode portions 424 a and 424 b are arranged.

In this embodiment, the electrode area EA may include a plurality ofelectrode areas divided with reference to the bus bar lines 42 b orleads 142. For example, the electrode area EA may include a firstelectrode area EA1 defined between two neighboring bus bar lines 42 b orleads 142, and two second electrode areas EA2 each defined between acorresponding one of the third and fourth edges 163 and 164 in the solarcell 150 and the lead 142 arranged adjacent thereto. In this embodiment,since a plurality of leads 142 (for example, six or more) is providedwith reference to one surface of the solar cell 150, a plurality offirst electrode areas EA1 may be provided (the number of first electrodeareas EA1 being smaller than the number of leads 142 by one).

In this instance, the width of each first electrode area EA1, forexample, a width W2, may be smaller than the width of each secondelectrode area EA2, for example, a width W3. In this embodiment, anumber of leads 142 or bus bar lines 42 b are provided. Accordingly, thewidth W3 of each second electrode area EA2 should be relatively great inorder to allow the inclined portions 163 b or 164 b of the third orfourth edge 163 or 164 to be disposed in the second electrode area EA2and, as such, it may be possible to prevent the bus bar lines 42 b orleads 142 from being disposed at the third or fourth edge 163 or 164. Ofcourse, the embodiment of the present invention is not limited to theabove-described conditions, and the width W2 of each first electrodearea EA1 and the width W3 of each second electrode area EA2 may havevarious values.

Meanwhile, the edge area PA may include first edge areas PA1 eachcorresponding to a region where each lead 142 is disposed, while beingdefined between neighboring finger lines 42 a, and second edge areas PA2corresponding to a remaining portion of the edge area PA, except for thefirst edge areas PA1, while being defined between outermost ones of thefinger lines 42 a and corresponding ones of the first to fourth edges161, 162, 163 and 164 of the semiconductor substrate 160, to provide apredetermined distance between the semiconductor substrate 160 and thefirst electrode 42. Each edge area PA1 may be arranged at a regionportion adjacent to the corresponding edge of the solar cell 150 in thecorresponding region where one lead 142 is disposed. Each first edgearea PA1 is an area defined to space a corresponding pad section 422 aapart from the corresponding edge of the solar cell 150, therebyenabling the corresponding lead 142 to be attached to the firstelectrode 42 by sufficient coupling force.

In this instance, the edge area PA may include a first end edge area PA3and a second end edge area PA4, which are arranged at opposite ends ofeach bus bar line 42 b between two adjacent electrode areas EAcorresponding to the bus bar line 42 b. The first end edge area PA3 isarranged at one end of the bus bar line 42 b adjacent to the first edge161 of the semiconductor substrate 160, whereas the second end edge areaPA4 is arranged at the other end of the bus bar line 42 b adjacent tothe second edge 162 of the semiconductor substrate 160. For example, thefirst end edge area PA3 may include the corresponding first edge areaPA1 arranged adjacent to the first edge 161, and a portion of thecorresponding second edge area PA2 (for example, a portion arrangedbetween the first edge area PA1 and the first edge 161 in the secondedge area PA2). In addition, the second end edge area PA4 may includethe corresponding first edge area PA1 arranged adjacent to the secondedge 162, and a portion of the corresponding second edge area PA2 (forexample, a portion arranged between the first edge area PA1 and thesecond edge 162 in the second edge area PA2).

In this instance, the first end edge area PA3 may be an area where anend of the corresponding lead 142 is disposed adjacent to the first edge161 of the semiconductor substrate 160. The lead 142 may extend toanother solar cell 150 or an external circuit after passing the secondend edge area PA4 and the second edge 162 of the semiconductor 160. Inthe specification, the terms “first end”, “second end”, “one end”, and“other end” are used to distinguish different elements from one another,and the embodiment of the present invention is not limited thereto.

The first electrode 42 may include a plurality of finger lines 42 aspaced apart from one another in the electrode area EA while having auniform width W5 and a uniform pitch P. In FIG. 9 , the finger lines 42a are illustrated as being formed to be parallel in a first directionwhile being parallel to the main edges of the solar cell 150 (forexample, the first and second edges 161 and 162). Of course, theembodiment of the present invention is not limited to theabove-described arrangement. In this instance, the finger lines 42 a mayinclude outermost finger lines 421 a and 421 b respectively disposedmost adjacent to the edges of the semiconductor substrate 160 (forexample, the first and second edges 161 and 162).

For example, the finger lines 42 a of the first electrode 42 may have awidth W5 of 35 to 120 μm. The finger lines 42 a of the first electrode42 may also have a pitch P of 1.2 to 2.8 mm. The number of finger lines42 a arranged in a direction crossing the finger lines 42 a may be 55 to130. The above-described width W5 and pitch P may be obtained undersimple process conditions. The width W5 and pitch P are defined tominimize shading loss caused by the finger lines 42 a while achievingeffective collection of current produced through photoelectricconversion. Each finger line 42 a may have a thickness of 5 to 50 μm.Such a thickness of the finger line 42 a may be easily obtained in aprocess of forming the finger line 42 a. In addition, the finger line 42a may have desired specific resistance in the above-described thicknessrange. Of course, the embodiment of the present invention is not limitedto the above-described conditions and, the width, pitch, thickness,etc., of the finger lines 42 a may be varied in accordance withvariation of process conditions, the size of the solar cell 150, thematerial of the finger lines 42 a, or the like.

In this instance, the width W1 of the leads 142 may be smaller than thepitch P of the finger lines 42 a while being greater than the width ofthe finger lines 42 a. Of course, the embodiment of the presentinvention is not limited to such conditions, and various variations arepossible.

In addition, the first electrode 42 may include at least bus bar lines42 b formed in a second direction crossing the finger lines 42 a in theelectrode area EA, to connect the finger lines 42 a. In the illustratedembodiment, each bus bar line 42 b may further include electrodeportions 424 a and 424 b disposed in corresponding ones of the firstedge areas PA1, respectively, while overlapping a corresponding one ofthe leads 142.

For example, each bus bar line 42 b may be formed to extend continuouslyfrom a region adjacent to the first edge 161 to a region adjacent to thesecond edge 162 in the electrode area EA. As described above, each busbar line 42 b may be disposed to correspond to a region where each lead142 is disposed to connect neighboring solar cells 150. The bus barlines 42 b may be provided to correspond to the leads 142 one to one. Inthis embodiment, accordingly, the bus bar lines 42 b are equal in numberto the leads 142 with reference to one surface of the solar cell 150. Inthis embodiment, each bus bar line 42 b may mean an electrode portion,which is disposed adjacent to the corresponding lead 142, and is formedto extend in a direction perpendicularly or inclinedly crossing thefinger lines 42 a while being connected to, contacting, or overlappingwith the corresponding lead 142.

Each bus bar line 42 b may include, in the electrode area EA, a linesection 421 extending lengthily in a direction that the correspondinglead 142 is connected to the bus bar line 42 b, while having arelatively small width, and pad sections 422 having a greater width thanthe line section 421, to increase a connection area to the correspondinglead 142. By virtue of the narrow line section 421, it may be possibleto minimize the area blocking light incident upon the solar cell 150. Byvirtue of the wide pad sections 422, it may be possible to enhanceattachment force between the lead 142 and the bus bar line 42 b whilereducing contact resistance. Each pad section 422 may have a greaterwidth than each line section 421 and, as such, is an area to which thecorresponding lead 142 is substantially attached. Each lead 142 may beattached to the corresponding line section 421. Alternatively, the lead142 may be simply laid on the line section 421 without being attached tothe line section 421.

The pad sections 422 may include first pad sections 422 a disposed atopposite ends of the line section 421 (for example, regions where thelead 142 is connected to the first electrode 42 or inner ends of thefirst and second end edge area PA3 and PA4) in the electrode area EA,and second pad sections 422 b disposed in an inside region of the busbar line 42 b, except for the first pad sections 422 a. As describedabove, force may be applied to the lead 142 at the ends of the linesection 421 or at the first pad sections 422 a in a direction away fromthe first electrode 42 (a direction away from the semiconductorsubstrate 160). Accordingly, when the first pad sections 422 a have agreater area than the second pad sections 422 b, strong attachment forcemay be provided between the lead 142 and the first electrode 42. In thisinstance, even when the first pad sections 422 a have a greater widththan the second pad sections 422 b, there is no remarkable effect inenhancing attachment force to the lead 142. In this regard, the firstpad sections 422 a may have a length L1 (a length measured in alongitudinal direction of the lead 142) greater than a length L2 of thesecond pad sections 422 b (a length measured in the longitudinaldirection of the lead 142).

The pad sections 422 may have a width (for example, the widths of thefirst pad sections 422 a and second pad sections 422 b) greater thanthose of the line section 421, extension sections 423, electrodeportions 424 a and 424 b, and finger lines 42 a. The pitch of the busbar lines 42 b may be greater than the pitch of the finger lines 42 a.

In this embodiment, the line sections 421 of the bus bar lines 42 b areillustrated as corresponding to respective leads 142. In more detail, inconventional instances, bus bar electrodes, which correspond to theleads 142 and have a much greater width than the finger lines 42 a, areprovided. In this embodiment, however, the line sections 421 of the busbar lines 42 b, which have a much smaller width than the bus barelectrodes, are provided. In this embodiment, each line section 421connects a plurality of finger lines 42 a and, as such, provides a path,along which bypass of carriers is carried out when a part of the fingerlines 42 a is short-circuited.

In the specification, the bus bar electrodes mean electrode portionsformed in a direction crossing the finger lines, to correspond torespective ribbons, while having a width corresponding to 12 times ormore (normally 15 times or more) the width of each finger line. Sincethe bus bar electrodes have a relatively great width, two or three busbar electrodes are formed at normal instances. Meanwhile, the linesections 421 of the bus bar lines 42 b in this embodiment may meanelectrode portions formed in a direction crossing the finger lines 42 a,to correspond to respective leads 142, while having a widthcorresponding to 10 times or less the width of each finger line 42 a.

For example, the width of the line section 421, for example, a width W4,may be 0.5 to 10 times the width of each finger line 42 a, for example,a width W5. When the ratio of the width W4 to the width W5 is 0.5 orless, effects of the line section 421 may be insufficient. On the otherhand, when the ratio is greater than 10, shading loss may be increasedbecause the width W4 of the line section 421 is excessively great. Forexample, in this embodiment, a number of line sections 421 is providedbecause a number of leads 142 is provided and, as such, shading loss maybe further increased. For example, the width W4 of the line section 421may be 0.5 to 7 times the width W5 of the finger line 42 a. When thewidth W4 of the line section 421 increases up to 7 times the width W5 ofthe finger line 42 a, it may be possible to further reduce shading loss.For example, the width W4 of the line section 421 may be 0.5 to 4 timesthe width W5 of the finger line 42 a, taking shading loss intoconsideration. For example, the width W4 of the line section 421 may be0.5 to 2 times the width W5 of the finger line 42 a. In this range,efficiency of the solar cell 150 may be greatly enhanced.

Meanwhile, the width W4 of the line section 421 may be equal to orsmaller than the width W1 of the lead 142. When the lead 142 has acircular, oval or round shape, the contact width or area of the lead 142contacting the line section 421 at a back surface thereof and, as such,the width W4 of the line section 421 may be equal to or smaller than thewidth W1 of the lead 142. When the width W4 of the line section 421 isrelatively small, it may be possible to reduce the material costs of thefirst electrode 42 through reduction of the area of the first electrode42.

For example, the ratio of the width W1 of the lead 142 to the width W4of the line section 421 may be 1:0.07 to 1:1. When the ratio is lessthan 1:0.07, electrical characteristics or the like may be degradedbecause the width W4 of the line section 421 is too small. On the otherhand, when the ratio is greater than 1:1, it may be impossible togreatly enhance contact characteristics to the line section 421 or thelike in spite of an increase in area of the first electrode 42. As aresult, shading loss, material costs, etc., may be increased. Forexample, the ratio may be 1:0.1 to 1:0.5 (for example, 1:0.1 to 1:0.3),taking into consideration shading loss, material costs, etc.

Meanwhile, the width W4 of the line section 421 may be 35 to 350 μm.When the width W4 of the line section 421 is less than 35 μm, electricalcharacteristics or the like may be degraded because the width W4 of theline section 421 is too small. On the other hand, when the width W4 ofthe line section 421 is greater than 350 μm, it may be impossible togreatly enhance contact characteristics to the line section 421 or thelike in spite of an increase in area of the first electrode 42. As aresult, shading loss, material costs, etc., may be increased. Forexample, the width W4 of the line section 421 may be 35 to 200 μm (forexample, 35 to 120 μm), taking into consideration shading loss, materialcosts, etc. The width W4 of the line section 421 connecting thecorresponding pad sections 422 may be 75 to 120 μm, taking electricalcharacteristics into consideration.

Of course, the embodiment of the present invention is not limited to theabove-described conditions and, the width W4 of the line section 421 maybe varied within a range capable of minimizing shading loss whileeffectively transferring current produced through photoelectricconversion.

Meanwhile, the width of each pad section 422, for example, a width W6,is greater than the width W4 of the line section 421 while being equalto or greater than the width W1 of the lead 142. Since the pad section422 is a section to achieve an enhancement in attachment force of thelead 142 through increase of a contact area thereof to the lead 142, thepad section 422 has a width greater than the width of the line section421 while being equal to or greater than the width of the lead 142.

For example, the ratio of the width W1 of the lead 142 to the width W6of the pad section 422 may be 1:1 to 1:5. When the ratio is less than1:1, attachment force between the pad section 422 and the lead 142 maybe insufficient because the width W6 of the pad section 422 isinsufficient. On the other hand, when the ratio is greater than 1:5,shading loss may be increased because the area of the pad section 422causing shading loss is increased. The ratio may be 1:2 to 1:4 (forexample, 1:2.5 to 1:4), taking into consideration attachment force,shading loss, etc.

Meanwhile, for example, the width W6 of the pad section 422 may be 0.25to 2.5 mm. When the width W6 of the pad section 422 is less than 0.25mm, attachment force between the pad section 422 and the lead 142 may beinsufficient because the contact area of the pad section 422 to the lead142 is insufficient. On the other hand, when the width W6 of the padsection 422 is greater than 2.5 mm, shading loss may be increasedbecause the area of the pad section 422 causing shading loss isincreased. For example, the width W6 of the pad section 422 may be 0.8to 1.5 mm.

Meanwhile, the pad section 422 may have lengths L1 and L2 of 2 to 30 mm.When the lengths L1 and L2 of the pad section 422 are less than 0.2 mm,attachment force between the pad section 422 and the lead 142 may beinsufficient because the contact area of the pad section 422 to the lead142 is insufficient. On the other hand, when the lengths L1 and L2 ofthe pad section 422 are greater than 30 mm, shading loss may beincreased because the area of the pad section 422 causing shading lossis increased.

In this instance, the length L1 of each first pad section 422 a, towhich greater force is applied, may be greater than the length L2 ofeach second pad section 422 b. For example, the length L1 of the firstpad section 422 a may be 0.4 to 30 mm. Taking shading loss intoconsideration, the length L1 of the first pad section 422 a may be 0.4to 5 mm. The length L2 of each second pad section 422 b may be 0.02 to 1mm. For example, the length L2 of the second pad section 422 b may be0.3 to 1 mm. Accordingly, attachment force obtained by the first padsection 422 a, to which greater force is applied, may be furtherincreased, and the area of the second pad section 422 b may be reducedand, as such, shading loss, material costs, etc. may be reduced.

For example, each pad section 422 may have a width of 0.5 to 2.0 mm anda length of 0.2 to 5 mm. In this instance, the widths of the first padsection 422 a and second pad section 422 b may be equal or differs fromeach other (to have a width difference of 10% or less), and the lengthof the first pad section 422 a is greater than the length of the secondpad section 422 b such that the area of the first pad section 422 a isgreater than the area of the second pad section 422 b. In this instance,accordingly, the length of the first pad section 422 a may be equal toor greater than the width of the first pad section 422 a (for example,the length of the first pad section 422 a is greater than the width ofthe first pad section 422 a), and the width of the second pad section422 b may be equal to or greater than the length of the second padsection 422 b (for example, the width of the second pad section 422 b isgreater than the length of the second pad section 422 b). For example,the first pad section 422 a has a width of 1.0 to 1.5 mm and a length of3.5 to 4.5 mm, and the second pad section 422 b has a width of 1.0 to1.5 mm and a length of 0.3 to 0.5 mm. Within such width and lengthranges, the first and second pad sections 422 a and 422 b may havemaximal effects.

Meanwhile, for example, the ratio of the width W5 of each finger line 42a to the lengths L1 and L2 of the pad section 422 may be 1:1.1 to 1:20.Within this range, the attachment area between the pad section 422 andthe lead 142 is increased and, as such, an attachment force between thepad section 422 and the lead 142 may be increased.

Meanwhile, for example, the ratio of the width W1 of the lead 142 to thelengths L1 and L2 of each pad section 422 may be 1:1 to 1:10. When theratio is less than 1:1, attachment force between the pad section 422 andthe lead 142 may be insufficient because the lengths L1 and L2 of thepad section 422 are insufficient. On the other hand, when the ratio isgreater than 1:10, shading loss may be increased because the area of thepad section 422 causing shading loss is increased. The ratio may be 1:3to 1:6, taking into consideration attachment force, shading loss, etc.

For one bus bar line 42 b, 6 to 24 (for example, 12 to 22) pad sections422 may be provided. The pad sections 422 may be arranged while beingspaced apart from one another by a certain distance. For example, onepad section 422 may be arranged per 2 to 10 finger lines 42 a. Inaccordance with this arrangement, regions where the contact area betweenthe bus bar line 42 b and the lead 142 increases are regularly providedand, as such, an attachment force between the bus bar line 42 b and thelead 142 may be increased. Alternatively, the pad sections 422 may bearranged such that the distance between adjacent ones of the padsections 422 is varied. For example, the pad sections 422 may bearranged in a higher density at end portions of the bus bar line 42 b,to which greater force is applied, as compared to the remaining portionof the bus bar line (for example, the central portion of the bus barline 42 b). Of course, various variations are possible.

Again referring to FIG. 7 , when a coating layer 142 b (a separatecoating layer for attachment of the lead 142 to the pad sections 422,for example, a soldering layer) is disposed in a region adjacent to eachpad section 422, the ratio of the width W1 of the lead 142 to the widthof the coating layer 142 b, for example, a width W7, may be 1:1 to1:3.33. Of course, the embodiment of the present invention is notlimited to the above-described conditions, and the ratio may havevarious values.

Meanwhile, the width W6 of each pad section 422 may be equal to orgreater than the width W7 of the coating layer 142 b in the regionadjacent to each pad section 422. For example, the width W7 of thecoating layer 142 b in the region adjacent to the pad section 422 to thewidth W6 of the pad section 422 may be 1:1 to 1:4.5. When the ratio isless than 1:1, bonding characteristics of the lead 142 and pad section422 may be inferior. On the other hand, when the ratio is greater than1:4.5, shading loss and manufacturing costs may increase because thearea of the pad section 422 increases.

Of course, the embodiment of the present invention is not limited to theabove-described conditions and, the width W6 and lengths L1 and L2 ofeach pad section 422 may have various values within a range capable ofenhancing attachment force of the pad section 422 to the lead 142through an increase in contact area of the pad section 422 to the lead142. Alternatively, it may be possible to separately provide the padsections 422.

Again referring to FIG. 9 , the first electrode 42 may further includethe extension sections 423, each of which divides the correspondingfirst edge area PA1 from the corresponding electrode area EA. Eachextension section 423 may extend from the corresponding end of thecorresponding line section 421 (or the corresponding pad section 422),and then reaches an outermost one of the corresponding finger lines 421a disposed adjacent to the corresponding first or second end edge areaPA3 or PA4 after extending along corresponding ends of the finger lines421 a. The extension section 423 may connect the ends of the fingerlines 42 a disposed adjacent to the first or second end edge area PA3 orPA4. When the extension sections 423 are provided, each extensionsection 423 functions to provide a path, along which carriers may flowwhen a part of the finger lines 42 a disposed at the corresponding firstor second end edge area PA3 or PA4 is short-circuited. In addition, theelectrode portions 424 a and 424 b disposed in each of the first andsecond end edge areas PA3 and PA4 may be connected to the correspondingfinger lines 42 a via the corresponding extension sections 423,respectively. Then, current collected by the finger lines 42 a disposedin the electrode area EA adjacent to the corresponding first or secondend edge area PA3 or PA4 may be transferred to the corresponding lead142 via the corresponding electrode portion 424 a or 424 b. Accordingly,current generated in the electrode area EA disposed adjacent to thefirst or second end edge area PA3 or PA4 may be effectively transferredto the electrode portion 424 a or 424 b. Of course, the embodiment ofthe present invention is not limited to such conditions, and theelectrode portion 424 a or 424 b in each first edge area PA1 may bedirectly connected to the corresponding finger lines 42 a without beingconnected to the corresponding extension sections 423. Other variationsmay also be possible.

The extension sections 423 may be inclinedly disposed on the fingerlines 42 a and bus bar line 42 b such that the width of the first edgearea PA1 is gradually increased toward a corresponding one of the firstand second edges 161 and 162 of the solar cell 150. For example, thefirst edge area PA1 may have an almost triangular shape. The twoextension sections 423 defining the first edge area PA1 may form analmost “V” shape. In accordance with such shapes, facing outer ends ofthe finger lines 42 a in two electrode areas EA adjacent to the firstedge area PA1 may be arranged to be gradually spaced farther apart fromeach other. In addition, the first edge area PA1 may have a shape with awidth gradually increasing toward the corresponding first or second edge161 or 162 of the solar cell 150 between the two electrode areas EA.Accordingly, the end portion of each electrode area EA adjacent to thefirst edge area PA1 may have a smaller width than the remaining portionof the electrode area EA. For example, the first edge area PA1 may havean isosceles triangle shape, and each electrode area EA may have analmost octagonal shape.

Accordingly, each lead 142 may be stably disposed in the correspondingedge areas PA1 without being attached to the corresponding extensionsections 423. In this embodiment, the end of each lead 142 not connectedto another solar cell 150 may extend to the inside of the correspondingfirst edge area PA1 after passing the corresponding end of the linesection 421 and, as such, may be disposed inside the first edge area PA1(or the corresponding first end edge area PA3). Accordingly, it may bepossible to stably fix the lead 142 to the end of the line section 421and, as such, the lead 142 may be fixed to the first electrode 42 bysufficient attachment force. On the other hand, when the end of the lead142 is disposed at the end of the line section 421, or does not reachthe end of the line section 421, the end of the lead 142 may be unstablyattached to the first pad section 422 a disposed at the end of the linesection 421. Meanwhile, when the end of the lead 142 extends to thecorresponding second edge area PA2, unnecessary short-circuit may begenerated.

For example, the length of a portion of the lead 142 disposed in eachfirst edge area PA1 may be greater than the length of a portion of thefirst edge area PA1 where the portion of the lead 142 is not disposed.That is, the ratio of a length L3 of the first edge area PA1 to a lengthL4 of the portion of the lead 142 disposed in the first edge area PA1may be 1:0.5 to 1:1. In this instance, the lead 142 may be stablyattached to the first pad section 422 a. For example, the ratio of thelength L3 of the first edge area PA1 to the length L4 of the portion ofthe lead 142 disposed in the first edge area PA1 may be 1:0.6 to 1:0.9.Within this range, the lead 142 may be stably attached to the first padsection 422 a while being prevented from extending to the correspondingsecond edge area PA2. Of course, the embodiment of the present inventionis not limited to the above-described conditions.

Meanwhile, the other end of the lead 142 may extend to the outside ofthe semiconductor substrate 160 after passing the corresponding firstedge area PA1 (or the corresponding second end edge area PA4). That is,the lead 142 may continuously extend from the corresponding first endedge area PA3 to the first pad section 422 a disposed adjacent to thecorresponding second end edge area PA4 after passing the first padsection 422 a disposed adjacent to the corresponding first end edge areaPA3, and may further extend to the outside of the semiconductorsubstrate 160 after passing the former first pad section 422 a and thesecond end edge area PA4.

In this instance, the lead 142 is structurally coupled or attached tothe corresponding pad sections 422. On the other hand, the lead 142 maybe structurally coupled or attached to the corresponding line section421 and/or the electrode portions 424 a and 424 b of the correspondingfirst and second end edge areas PA3 and PA4 or may be maintained withoutbeing structurally coupled or attached thereto. Although the lead 412 ismaintained without being structurally coupled or attached to thecorresponding line section 421 and/or the electrode portions 424 a and424 b of the corresponding first and second end edge areas PA3 and PA4,the lead 142 may be connected (for example, electrically connected)thereto in accordance with overlap and contact therebetween. This isbecause the coating layer 142 b of the lead 142, which includes a soldermaterial, may be hardly attached to the line section 421 and/or theelectrode portions 424 a and 424 b.

For this reason, the coupling force between the bus bar line 42 b andthe lead 142 in the first and second end edge areas PA3 and PA4 may besmaller than the coupling force between the bus bar line 42 b and thelead 142 in an area except for the first and second end edge areas PA3and PA4. For example, the coupling force between the electrode portions424 a and 424 b of the bus bar line 42 b and the lead 142 in the firstand second end edge areas PA3 and PA4 may be smaller than the couplingforce between each pad section 422 (for example, each first pad section422 a) and the lead 142. Accordingly, sufficient coupling force may beobtained by the pad sections. In addition, reliable electricalconnection may be achieved in the first and second end edge areas PA3and PA4, even though a small electrode area is provided.

The width of each first edge area PA1 disposed between the correspondingoutermost finger lines 421 a and 421 b (or the width of the first orsecond end edge area PA3 or PA4), for example, a width W8, may begreater than the width W1 of the lead 142. Accordingly, the lead 142 maybe stably disposed in the first edge area PA1. For example, the lead 142may be maintained in the first edge area PA1 even when the lead 142 islaterally bent within the first edge area PA1 during a process ofattaching the lead 142.

The width W8 of the first edge area PA1 may be 0.73 to 3.8 mm. Forexample, the width W8 of the first edge area PA1 may be 0.73 to 2 mm.Meanwhile, the ratio of the width W1 of the lead 142 to the width of thefirst edge area PA1 may be 1:1.46 to 1:15.2 (for example, 1:1.46 to1:5). Within this range, the lead 142 may be stably disposed in thefirst edge area PAL

Meanwhile, assuming that “L” represents the width W8 of the first edgearea PA1, and “D” represents an edge distance, “L” and “D” may satisfythe following Expression 1. Here, the edge distance D means the distancebetween an inner end of the first edge area PA1 disposed inwards of thecorresponding outermost finger lines 421 a or 421 b (or the pad section422 disposed at the inner end) and the edge of the solar cell 150adjacent to the end of the first electrode 42 (for example, the first orsecond edge 161 or 162) in a region where the lead 142 is disposed.0.9*(0.1569*D+0.3582)≤L≤1.1*(0.1569*D+0.3582)  <Expression 1>(Here, the unit of “L” is mm, and the unit of “D” is mm.)

The above Expression 1 is based on the fact that the width W8 of thefirst edge area PA1 should be sufficiently great when the edge distanceD is great, because a phenomenon in which the lead 142 is bent mayincrease when the edge distance D increases. Of course, the embodimentof the present invention is not limited to the above-describedconditions.

The width of each extension section 423 is smaller than the width of theline section 421. For example, the width of the line section 421 mayhave a value corresponding to 2 times or more the width of eachextension section 423. Then, the sum of the widths of two extensionsections 423 in a region where the two extension sections 423 arebranched from the line section 421 is equal to or smaller than the widthof the line section 421. Accordingly, it may be possible to minimize thewidth of each extension section 423 while preventing the width of thebus bar line 42 b from being increased in a region where the twoextension sections 423 are connected to the line section 421. Forexample, the width W4 of the line section 421 may be 2 to 10 times thewidth of each extension sections 423. Meanwhile, for example, the linewidth of each extension section 423 may be 35 to 120 μm.

Meanwhile, the width of each extension section 423 may be smaller thanthe width of each finger line 42 a or may be equal or similar thereto.For example, the width of each extension section 423 may be 2 times orless (for example, 0.5 to 2 times) the width of each finger line 42 a.In this instance, it may be possible to avoid an increase in shadingloss caused by the extension sections 423 while achieving effects of theextension sections 423. Of course, the embodiment of the presentinvention is not limited to the above-described conditions and, eachextension section 423 may have various widths in a range capable ofconnecting the corresponding finger lines 42 a, thereby achieving flowof current.

Meanwhile, in this embodiment, each bus bar line 42 b may include theelectrode portions 424 a and 424 b respectively disposed at thecorresponding first and second end edge areas PA3 and PA4. Each lead 142overlaps with or contacts the electrode portions 424 a and 424 brespectively disposed at the corresponding first and second end edgeareas PA3 and PA4 or may be electrically connected thereto. Accordingly,the electrode portions 424 a and 424 b function as a path, along whichcurrent flows to the lead 142. In this regard, it may be understood thatthe electrode portions 424 a and 424 b constitute a part of the bus barline 424 b.

In this embodiment, current generated at the electrode areas EA disposedadjacent to the first and second end edge areas PA3 and PA4 may betransferred to the corresponding lead 142 via the electrode portions 424a and 424 b disposed at the first and second end edge areas PA3 and PA4.Accordingly, it may be possible to effectively transfer currentgenerated at portions of the electrode areas EA respectively disposedadjacent to the first and second end edge areas PA3 and PA4 (forexample, a portion of the electrode area EA disposed between two firstedge areas PA3 disposed in parallel while extending in parallel with thefinger lines 42 a and/or a portion of the electrode area EA disposedbetween two second edge areas PA4 disposed in parallel while extendingin parallel with the finger lines 42 a) to the corresponding lead 142 bythe corresponding electrode portions 424 a and 424 b. Accordingly, evenwhen the first edge areas PA1 (or the first and second end edge areasPA3 and PA4) are provided to achieve an enhancement in the bonding forceor coupling force of the leads 142, it may be possible to avoid anefficiency reduction that may be caused by the provision of the firstedge areas PA1. Thus, the efficiency of the solar cell 150 may beenhanced and, as such, the output power of the solar cell panel 100 maybe enhanced.

When the electrode portions 424 a and 424 b are not provided at thefirst and second end edge areas PA3 and PA4, differently than thisembodiment, current generated at portions of the electrode area EArespectively disposed adjacent to the first and second end edge areasPA3 and PA4 is transferred to the corresponding lead 142 after beingcollected at the corresponding first pad sections 422 a. In thisinstance, however, it may be difficult to effectively collect currentgenerated at the portions of the electrode area EA respectively disposedadjacent to the first and second end edge areas PA3 and PA4.

To this end, in this embodiment, the electrode portions 424 a and 424 bare provided. The electrode portions 424 a and 424 b may achieve desiredeffects, so long as the electrode portions 424 a and 424 b have shapesconnectable to the corresponding finger lines 42 a, bus bar line 42 b orlead 142. In this instance, the electrode portions 424 a and 424 b arearranged at the first and second end edge areas PA3 and PA4 in a lowerdensity than that of the finger lines 42 a in the electrode area EA.

For example, the first and second end edge areas PA3 and PA4 may beformed to be symmetrical with reference to a central line of thesemiconductor substrate 160 (for example, a central line parallel to thefinger lines 42 a). Thus, in this embodiment, the first end edge areasPA3 and the second end edge areas PA4 are provided at opposite edges ofthe semiconductor substrate 160 (for example, the first and second edges161 and 162), respectively, and, as such, it may be possible toeffectively prevent a reduction in attachment force of the leads 142that may occur at the opposite edges of the semiconductor substrate 160.

In this embodiment, the electrode portion 424 a disposed at each firstend edge area PA3 may include an opening formed through the electrodeportion 424 a. In this instance, the outermost end of the electrodeportion 424 a may extend to be flush with the outermost finger lines 421a disposed adjacent thereto or may extend outwards beyond the outermostfinger lines 421 a (to be closer to the first edge 161 of thesemiconductor substrate 160). Similarly, the electrode portion 424 bdisposed at each second end edge area PA4 may include an opening formedthrough the electrode portion 424 b. In this instance, the outermost endof the electrode portion 424 b may extend to be flush with the outermostfinger lines 421 b disposed adjacent thereto or may extend outwardsbeyond the outermost finger lines 421 b (to be closer to the second edge162 of the semiconductor substrate 160). Accordingly, the electrodeportions 424 a and 424 b may be stably connected to the correspondinglead 142. Thus, it may be possible to more stably transfer currentgenerated at portions of the electrode area EA respectively disposedadjacent to the first and second end edge areas PA3 and PA4 to the lead142.

Since each of the electrode portions 424 a and 424 b disposed at thefirst and second end edge areas PA3 and PA4 has an opening (a portionwhere no electrode is formed), as described above, it may be possible toachieve reliable connection between the electrode portions 424 a and 424b and the corresponding finger lines 42 a, even though the electrodeportions 424 a and 424 b are formed in a lower density than that ofelectrode portions disposed in the electrode area EA. In addition, theoutermost ends of the electrode portions 424 a and 424 b (for example,outermost ends of second electrode parts 4242 and 4243) may be disposedto be flush with the outermost finger lines 421 a and 421 b disposedadjacent thereto, respectively, or may be disposed outwards of theoutermost finger lines 421 a and 421 b, respectively, and, as such,current collected at the side of outer finger lines 42 a disposedadjacent to the first or second end edge area PA3 or PA4 may beeffectively transferred to the corresponding lead without remaining atthe outer finger lines 42 a.

Meanwhile, in this embodiment, the electrode portion 424 a disposed ateach first end edge area PA3 and the electrode portion 424 b disposed ateach second end edge area PA4 have different shapes (for example,asymmetrical shapes). In this instance, accordingly, the opening of theelectrode portion 424 a disposed at each first end edge area PA3 and theopening of the electrode portion 424 b disposed at each second end edgearea PA4 may have different shapes or different arrangements. Asdescribed above, one end of each lead 142 is disposed at thecorresponding first end edge area PA3, and the other end of the lead 142extends to the outside of the semiconductor substrate 160 beyond thecorresponding second end edge area PA4. Accordingly, the length of theportion of the lead 142 disposed at the first end edge area PA3 differsfrom the length of the portion of the lead 142 disposed at the secondend edge area PA4. For example, the length of the portion of the lead142 disposed at the second end edge area PA4 is greater than the lengthof the portion of the lead 142 disposed at the first end edge area PA3.Taking this condition into consideration, the electrode portion 424 adisposed at the first end edge area PA3 and the electrode portion 424 bdisposed at the second end edge area PA4 are configured to havedifferent shapes.

For example, the electrode portion 424 a disposed at the first end edgearea PA3 may include a first electrode part 4241 disposed inwards of theoutermost finger lines 421 a disposed adjacent to the first end edgearea PA3, and a second electrode part 4242 extending from the firstelectrode part 4241 to a position flush with the outermost finger lines421 a or a position outwards of the outermost finger lines 421 a in adirection crossing the first electrode part 4241.

In this instance, the first electrode part 4241 may be connected (forexample, directly connected or connected via the corresponding extensionsections 423) to the finger lines 42 a disposed within portions of theelectrode areas EA respectively arranged at opposite sides of the firstend edge area PA3 while extending in parallel with the finger lines 42 aof the electrode areas EA or crossing (for example, perpendicularlycrossing) the line section 421 of the corresponding bus bar line 42 b.In this instance, since the first electrode part 4241 is connected tothe finger lines 42 a disposed within the portions of the electrodeareas EA respectively arranged at opposite sides of the first end edgearea PA3, current generated at the portions of the electrode areas EAmay be transferred to the first electrode part 4241. In this instance,the opening of the electrode portion 424 a is defined by the firstelectrode part 4241, the first pad section 422 a disposed at the innerend of the corresponding first edge area PA1, and the extension sections423 disposed at the first edge area PA1.

Meanwhile, the second electrode part 4242 may cross (for example,perpendicularly cross) the finger lines 42 a or may be parallel to theline section 421 of the corresponding bus bar line 42 b. The secondelectrode part 4242 extends from the first electrode part 4241, which isspaced apart from the corresponding first pad 422 a of the bus bar line42 b, and, as such, it may be possible to prevent the second electrodepart 4242 from unnecessarily interfering with the first pad 422 a tohave increased coupling force to the corresponding lead 142. Inaddition, it may be possible to achieve a reduction in electrode areaand, as such, material costs may be reduced. The second electrode part4242 is disposed to pass through the center of the first electrode part4241 and, as such, the connection area or connection reliability of thefirst electrode part 4241 to the lead 142 may be greatly increased.Accordingly, current transferred via the first electrode part 4241 maybe stably transferred to the lead 142.

In accordance with the above-described arrangement, a kind of an openingis formed among one side of the first electrode part 4241 (a left sidein the drawings), a portion of the second electrode part 4242 disposedadjacent to one side of the first electrode part 4241, and the firstedge 161. Similarly, a kind of an opening is formed among the other sideof the first electrode part 4241, a portion of the second electrode part4242 disposed adjacent to the other side of the first electrode part4241, and the first edge 161.

In this instance, for example, the first electrode part 4241 in eachfirst edge area PA1 may be positioned to be closer to the correspondingoutermost finger lines 421 a or 421 b than the inner end of the firstedge area PA1 in a direction parallel to the corresponding line section421. That is, the ratio of the length L3 of the first edge area PA1 tothe distance between the first electrode part 4241 and the first pad 422a corresponding thereto may be 1:0.5 to 1:1. For example, the ratio ofthe length L3 of the first edge area PA1 to the distance between thefirst electrode part 4241 and the first pad 422 a may be 1:0.6 to 1:0.9.In this instance, when the lead 142 extends to a position on the secondelectrode part 4242 while crossing the first electrode part 4241, thelead 142 may be stably attached to the first pad 422 a while passing thefirst pad 422 a. In addition, it may be possible to prevent the lead 142from extending to the corresponding second edge area PA2. Of course, theembodiment of the present invention is not limited to theabove-described conditions.

The electrode portion 424 b in each second end edge area PA4 may includea third electrode part 4243 disposed at a position flush with thecorresponding outermost finger lines 421 b or a position outwards of theoutermost finger lines 421 b. In this instance, the corresponding lead142 may extend to the outside of the semiconductor substrate 160 whilecrossing the third electrode part 4243. In this instance, the thirdelectrode part 4243 may be formed to be parallel to the finger lines 42a or to cross (for example, perpendicularly cross) the line section 421of the corresponding bus bar line 42 b, and may be connected (forexample, directly connected or connected via the corresponding extensionsections 423) to the finger lines 42 a disposed within portions of theelectrode areas EA respectively arranged at opposite sides of the secondend edge area PA4.

In this instance, since the third electrode part 4243 is connected tothe finger lines 42 a disposed within the portions of the electrodeareas EA respectively arranged at opposite sides of the second end edgearea PA4, current generated at the portions of the electrode areas EAmay be transferred to the first electrode part 4241 via the thirdelectrode part 4243. In the second edge area PA4, the lead 142 extendsto the outside of the semiconductor substrate 160. Accordingly, althoughthe electrode portion 424 b only includes the third electrode part 4243,the lead 142 may be stably connected to the corresponding finger lines42 a. Thus, it may be possible to simplify the structure of theelectrode portion 424 b in the second end edge area PA4 and, as such,reduction in manufacturing costs and simplification of the manufacturingprocess may be achieved. In accordance with the above-describedconfiguration, an opening is formed among the third electrode part 4243,the first pad section 422 a disposed at the inner end of the first edgearea PA1, and the extension sections 423 disposed at the first edge areaPA1. In this instance, the distance between the third electrode part4243 and the first pad section 422 a disposed adjacent thereto isgreater than the distance between the first electrode part 4241 and thefirst pad section 422 a disposed adjacent thereto. Accordingly, theopening formed between the third electrode part 4243 and the first padsection 422 a corresponding thereto while being disposed at the secondend edge area PA4 may have a greater area than the opening formedbetween the first electrode part 4241 and the first pad section 422 acorresponding thereto while being disposed at the first end edge areaPA3.

In the drawings, the electrode portions 424 a and 424 b are illustratedas being disposed at positions flush with the corresponding outermostfinger lines 421 a and 421 b or extending to the positions,respectively. Of course, the embodiment of the present invention is notlimited to the above-described conditions, and the electrode portions424 a and 424 b may extend to protrude beyond the outermost finger lines421 a and 421 b, respectively, as illustrated in FIGS. 13 to 15 . Thiswill be described later in more detail.

As described above, in this embodiment, in each first end edge area PA3,the second electrode part 4242, which extends in a direction parallel tothe corresponding line section 421, is disposed at a position flush withthe corresponding outermost finger lines 421 a or a position outwards ofthe outermost finger lines 421 a. On the other hand, in each second endedge area PA4, the third electrode part 4243, which extends in adirection crossing the corresponding line section 421, is disposed at aposition flush with the corresponding outermost finger lines 421 b or aposition outwards of the outermost finger lines 421 b. Such anarrangements are implemented, taking into consideration the conditionsthat one end of the lead 142 is disposed within the first end edge areaPA3, and the lead 142 extends to the outside of the semiconductorsubstrate 160 while crossing the second end edge area PA4. In accordancewith the above-described arrangements, it may be possible to stablyconnect the lead 142 to the electrode portions 424 a and 424 b, evenwhen the arrangement of the lead 142 is varied.

The width of the electrode portions 424 a and 424 b disposed withinrespective edge areas PA may be greater than the width of the fingerlines 42 a or may be equal to or similar to the width of the fingerlines 42 a. The width of the electrode portions 424 a and 424 b may alsobe smaller than the pitch of the finger lines 42 a. For example, thewidth of the electrode portions 424 a and 424 b may be 2 times or less(for example, 0.5 to 2 times) the width of the finger lines 42 a.Alternatively, the width of the leads 142 may be greater than the widthsof the electrode portions 424 a and 424 b. In addition, ratios of thewidth of the finger lines 42 a to widths of other electrode portions andthe width, pitch, etc., of the leads 142 may be applied to ratios of thewidth of the electrode portions 424 a and 424 b to the widths of theother electrode portions and the width, pitch, etc., of the leads 142 inthe same manner. Accordingly, it may be possible to avoid problemscaused by the electrode portions 424 a and 424 b such as an increase inshading loss while achieving effects by the provision of the electrodeportions 424 a and 424 b. Of course, the embodiment of the presentinvention is not limited to the above-described conditions, and theelectrode portions 424 a and 424 b may be satisfied, so long as theelectrode portions 424 a and 424 b have a width range capable ofachieving smooth flow of current.

In this embodiment, each bus bar line 42 b may have a thickness of 3 to45 μm. Within this thickness range, the bus bar line 42 b may be easilyformed, and may have a desired specific resistance. Of course, theembodiment of the present invention is not limited to theabove-described conditions and, the thickness of the bus bar line 42 bor the like may be varied in accordance with variations of processconditions, size of the solar cell 150, the material of the bus bar line42 b, etc.

In this embodiment, the finger lines 42 a and the bus bar lines 42 b maybe formed as different layers, respectively. That is, the finger lines42 a may be constituted by a layer different from that of the linesections 421, pad sections 422, and electrode portions 424 a and 424 bconstituting the bus bar lines 42 b. The extension sections 423 mayconstitute portions of the corresponding finger line 42 a and, as such,may be formed as the same layer as the finger line 42 a. Alternatively,the extension sections 423 may constitute portions of the correspondingbus bar line 42 b and, as such, may be formed as the same layer as thebus bar line 42 b. For example, as illustrated in an enlarged uppercircle of FIG. 9 , the bus bar lines 42 b are first formed, and thefinger lines 42 a are then formed to be disposed over the bus bar lines42 b such that the finger lines 42 a corresponding to each bus bar lines42 b overlap at least a portion of the corresponding bus bar line 42 b.In this embodiment, the finger lines 42 a disposed at one side (forexample, a left side of FIG. 9 ) of each bus bar line 42 b and thefinger lines 42 a disposed at the other side (for example, a right sideof FIG. 9 ) of the bus bar line 42 b are spaced apart from each other.On the bus bar line 42 b, accordingly, there is a region where no fingerline 42 a is formed and, as such, manufacturing costs may be minimizedin association with formation of the finger lines 42 a. Of course, theembodiment of the present invention is not limited to theabove-described conditions and, the finger lines 42 a may be disposed tocross the entire portion of the bus bar line 42 b.

The finger lines 42 a and the bus bar lines 42 b may be made of the samematerial or different materials. For example, when the finger lines 42 aand bus bar lines 42 b are formed by printing, a paste for forming thebus bar lines may have relatively low viscosity, whereas a paste forforming the finger lines 42 a may have relatively high viscosity. Inthis instance, accordingly, after curing, the bus bar lines have agreater thickness than the finger lines 42 a. In this regard, when thefinger lines 42 a are formed after formation of the bus bar lines 42 b,as described above, more stable formation thereof may be achieved.

For example, the paste for forming the finger lines 42 a may have agreater content of metal (for example, silver) than the paste forforming the bus bar lines 42 b. In this instance, the resistance of thefinger lines 42 a directly associated with collection of carriers may bereduced and, as such, an enhancement in carrier collection efficiencymay be achieved. In addition, a reduction in manufacturing costs may beachieved in accordance with a reduction in metal content of the bus barlines 42 b.

Meanwhile, the finger lines 42 a of the first electrode 42 may be formedto extend through the passivation film 22 and anti-reflective film 24,and the bus bar lines 42 b may be formed on the passivation film 22 andanti-reflective film 24. In this instance, openings (designated byreference numeral “102” in FIG. 3 ) having a shape corresponding to thefinger lines 42 may be formed in regions where no bus bar line 42 b isformed. That is, the openings are not formed in regions where the busbar lines 42 b are formed. In this instance, the first-conduction-typeconductive region 20 may have a shape corresponding to regions where theopenings 102 are formed. That is, in the electrode area EA, thefirst-conduction-type conductive region 20 may be formed to have a shapecorresponding to the finger lines 42 a, without being formed in regionscorresponding to the bus bar lines 42 b. In this instance, the linesection 421, pad sections 422 and electrode portions 424 a and 424 bconstituting each bus bar line 42 b (the extension sections 423 beingalso included when the extension sections 423 constitute portions of thebus bar line 42 b) are formed on the passivation film 22 andanti-reflective film 24, and the first-conduction-type conductive region20 may not be formed in regions corresponding to the sections 421, 422,424 a and 424 b of each bus bar line 42 b. Then, the line section 421and pad sections 422 of each bus bar line 42 b (the extension sections423 being also included when the extension sections 423 constituteportions of the bus bar line 42 b) may constitute a floating electrode.

Of course, the embodiment of the present invention is not limited to theabove-described conditions and, the bus bar lines 42 b may be formedafter formation of the finger lines 42 a. Alternatively, the fingerlines 42 a and the bar lines 42 b may be simultaneously formed through asingle process, using the same material, and, as such, may take the formof a single layer, as illustrated in an enlarged lower circle of FIG. 9. Other variations are possible.

Meanwhile, the first electrode 42 may further include edge lines 42 ceach connected to an end of a corresponding one of the outermost fingerlines 421 a and 421 b disposed adjacent to a corresponding one of thethird and fourth edges 163 and 164 while dividing a corresponding one ofthe second edge areas PA2 from the electrode area EA. Each edge line 42c may be spaced apart from the corresponding third or fourth edge 163 or164 by a uniform distance in a region adjacent to the correspondingthird or fourth edge 163 or 164 while having a shape identical orsimilar to that of the corresponding third or fourth edge 163 or 164. Inthis instance, each edge line 42 c connects the ends of the finger lines42 a adjacent to the corresponding third or fourth edge 163 or 164.

The second edge areas PA2 may be arranged between the edge lines 42 cand the third and fourth edges 163 and 164 and between the first andsecond edges 161 and 162 and the outermost finger lines 421 a and 421 badjacent to the first and second edges 161 and 162, respectively, totake the form of a frame. Each second edge area PA2 may have a width W9of 0.5 to 1.5 mm. When the width W9 of the second edge area PA2 is lessthan 0.5 mm, unnecessary shunting may occur. On the other hand, when thewidth W9 of the second edge area PA2 is greater than 1.5 mm, the area ofan ineffective region may increase and, as such, efficiency of the solarcell 150 may be insufficient. Of course, the embodiment of the presentinvention is not limited to the above-described conditions.

The width of each edge line 42 c may be equal or similar to the width ofeach finger line 42 a. The width and thickness of each finger line 42 aand relations of each finger line 42 a with other electrode sections andthe lead 142 may be applied to the edge lines 42 c in the same manner.For example, the edge line 42 c may constitute portions of thecorresponding finger lines 42 a.

In this embodiment, when “W” represents the width W1 of the lead 142,and “D” represents the edge distance, “W” and “D” may satisfy thefollowing Expression 2.13.732*In(W)−71.436−0.0000321462*(W)2≤D≤13.732*In(W)−71.436+0.0000321462*(W)2  <Expression2>(Here, the unit of “W” is μm, and the unit of “D” is mm.)

As described above, force is applied, in a direction away from the solarcell 150, to the lead 142 at the first pad section 422 a of the firstelectrode 42 where the lead 142 is disposed and, as such, an attachmentforce between the lead 142 and the first electrode 42 may be reduced.That is, as illustrated in FIG. 10 , when the width W1 of the lead 142increases, the bending degree of the solar cell 150 or semiconductorsubstrate 160 is increased. For reference, in FIG. 10 , “300 Wire”corresponds to the instance in which the width W1 of the lead 142 is 300μm, “330 Wire” corresponds to the instance in which the width W1 of thelead 142 is 330 μm, and “400 Wire” corresponds to the instance in whichthe width W1 of the lead 142 is 400 μm. When the width W1 of the lead142 increases, greater force is applied to the lead 142 at the first padsection 422 a of the first electrode 42 in a direction away from thesolar cell 150 and, as such, an attachment force between the lead 142and the first electrode 42 may be reduced. In order to prevent suchattachment force reduction, the edge distance D is sufficiently securedin this embodiment, to minimize stress applied to the first electrode42.

That is, the inventors found that, when the width W1 of the lead 142increases, it may be possible to provide sufficient attachment forcebetween the lead 142 and the first electrode 42 by increasing the edgedistance D, and then proposed the range of the edge distance D accordingto the width W1 of the lead 142 as expressed in Expression 2. In thisconnection, the lead 142 is connected to the first pad section 422 a ata sufficient area while having sufficient coupling force, as describedabove, and, as such, the distance between the first pad section 422 aand the corresponding edge of the semiconductor substrate 160 is definedas the edge distance D.

For example, the inventors measured the attachment force of the lead1422 at the first pad section 422 a of the first electrode 42 whilevarying the width W1 of the lead 142 and the edge distance D. Duringmeasurement, instances in which attachment force having a predeterminedvalue or more (for example, 1.5N or more, more preferably, 2N or more)is exhibited were sought, and instances having the predetermined valueor more were marked in FIG. 11 , using a mark “x”. Thereafter, a rangeof the edge distance D according to the width W1 of the lead 142 wheremarks “x” are located was sought and, as such, the above Expression 2 asto lower and upper limits of the edge distance D was derived.

When the edge distance D is within the range expressed by the aboveExpression 2 under the condition that the width W1 of the lead 142 has aconstant value, the lead 142, which has a wire shape, may be maintainedin a state of being stably attached to the ends of the first electrode42. In this embodiment, accordingly, it may be possible not only toachieve various effects according to use of the lead 142, which has awire shape, but also to enhance the attachment force of the lead 142through adjustment of the edge distance D.

Since the width W1 of the lead 142 is 250 to 500 μm, the edge distance Dmay have a value of 2.37 to 21.94 mm. For example, when the width W1 ofthe lead 142 is equal to or greater than 250 μm, but less than 300 μm,the edge distance D may be 2.37 to 9.78 mm. When the width W1 of thelead 142 is equal to or greater than 300 μm, but less than 350 μm, theedge distance D may be 3.99 to 12.94 mm. When the width W1 of the lead142 is equal to or greater than 350 μm, but less than 400 μm, the edgedistance D may be 5.06 to 15.98 mm. When the width W1 of the lead 142 isequal to or greater than 400 μm, but less than 450 μm, the edge distanceD may be 5.69 to 18.96 mm. When the width W1 of the lead 142 is equal toor greater than 450 μm, but not greater than 500 μm, the edge distance Dmay be 5.94 to 21.94 mm. In the above-described ranges, Expression 2 issatisfied and, as such, superior attachment force may be provided.

For example, when the width W1 of the lead 142 is equal to or greaterthan 250 μm, but less than 300 μm, the edge distance D may be 4 to 9.78mm. When the width W1 of the lead 142 is equal to or greater than 300μm, but less than 350 μm, the edge distance D may be 6 to 12.94 mm. Whenthe width W1 of the lead 142 is equal to or greater than 350 μm, butless than 400 μm, the edge distance D may be 9 to 15.98 mm. When thewidth W1 of the lead 142 is equal to or greater than 400 μm, but lessthan 450 μm, the edge distance D may be 10 to 18.96 mm. When the widthW1 of the lead 142 is equal to or greater than 450 μm, but not greaterthan 500 μm, the edge distance D may be to 21.94 mm. In theabove-described ranges, sufficient attachment force may be more stablyprovided. For example, in this embodiment, when the width W1 of the lead142 is equal to or greater than 350 μm, but less than 400 μm, the edgedistance D may be 9 to 15.98 mm. In this instance, the output power ofthe solar cell panel 100 may be maximized. Of course, the embodiment ofthe present invention is not limited to the above-described conditions.

In this embodiment, the edge distance D between each first pad section422 a and a corresponding one of the first and second edges 161 and 162may satisfy the above Expression 2 because the first pad section 422 ais arranged at the corresponding end of the bus bar line 42 b where thelead 142 is disposed.

The inventors also found that the number of leads 142 (the number of busbar lines 42 b) arranged at one surface of the solar cell 150 relates tothe width W1 of each lead 142. FIG. 12 is a diagram depicting outputs ofthe solar cell panel 100 measured while varying the width of each lead142 and the number of leads 142. Referring to FIG. 12 , it may be foundthat, when 6 to 33 leads 142 having a width W1 of 250 to 500 μm areprovided, the output power of the solar cell panel 100 exhibits asuperior value. In this instance, it may be found that, when the widthW1 of each lead 142 increases, the required number of leads 142 may bereduced.

For example, when the width W1 of the lead 142 is equal to or greaterthan 250 μm, but less than 300 μm, the number of leads 142 (withreference to one surface of the solar cell 150) may be 15 to 33. Whenthe width W1 of the lead 142 is equal to or greater than 300 μm, butless than 350 μm, the number of leads 142 may be 10 to 33. When thewidth W1 of the lead 142 is equal to or greater than 350 μm, but lessthan 400 μm, the number of leads 142 may be 8 to 33. When the width W1of the lead 142 is equal to or greater than 400 μm, but not greater than500 μm, the number of leads 142 may be 6 to 33. Meanwhile, when thewidth W1 of the lead 142 is equal to or greater than 350 μm, it may bedifficult to further increase the output power of the solar cell panel100 even though the number of leads 142 exceeds 15. When the number ofleads 142 increases, load on the solar cell 150 may be increased. Inthis regard, when the width W1 of the lead 142 is equal to or greaterthan 350 μm, but less than 400 μm, the number of leads 142 may be 8 to15. In addition, when the width W1 of the lead 142 is equal to orgreater than 400 μm, but not greater than 500 μm, the number of leads142 may be 6 to 15. In order to further enhance the output power of thesolar cell panel 100, the number of leads 142 may be equal to or greaterthan 10 (for example, 12 to 13). Of course, the embodiment of thepresent invention is not limited to the above-described conditions and,the number of leads 142 and the number of bus bar lines 42 b may havevarious values.

Meanwhile, the pitch of leads 142 (or the pitch of bus bar lines 42 b)may be 4.75 to 26.13 mm. This pitch is determined, taking intoconsideration the width W1 of each lead 142 and the number of leads 142.For example, when the width W1 of the lead 142 is equal to or greaterthan 250 μm, but less than 300 μm, the pitch of leads 142 may be 4.75 to10.45 mm. When the width W1 of the lead 142 is equal to or greater than300 μm, but less than 350 μm, the pitch of leads 142 may be 4.75 to15.68 mm. When the width W1 of the lead 142 is equal to or greater than350 μm, but less than 400 μm, the pitch of leads 142 may be 4.75 to19.59 mm. When the width W1 of the lead 142 is equal to or greater than400 μm, but not greater than 500 μm, the pitch of leads 142 may be 10.45to 26.13 mm. For example, when the width W1 of the lead 142 is equal toor greater than 350 μm, but less than 400 μm, the pitch of leads 142 maybe 10.45 to 19.59 mm. When the width W1 of the lead 142 is equal to orgreater than 400 μm, but not greater than 500 μm, the pitch of leads 142may be 10.45 to 26.13 mm. Of course, the embodiment of the presentinvention is not limited to the above-described conditions, and thepitch of leads 142 and the pitch of bus bar lines 42 b may have variousvalues.

In this embodiment, the first electrode 42, leads 142, electrode areaEA, edge area PA, etc., may be symmetrically arranged in a lateraldirection (a direction parallel to the finger lines 42 a) and a verticaldirection (a direction parallel to the bus bar lines 42 b or leads 142).In accordance with this arrangement, stable current flow may beachieved. Of course, the embodiment of the present invention is notlimited to the above-described arrangement.

The above description has been given mainly in conjunction with thefirst electrode 42 with reference to FIGS. 9 to 12 . The secondelectrode 44 may include finger lines, bus bar lines and edge linesrespectively corresponding to the finger lines 42 a, bus bar lines 42 band edge lines 42 c of the first electrode 42. The descriptions given ofthe finger lines 42 a, bus bar lines 42 b and edge lines 42 c of thefirst electrode 42 may be applied to the finger lines, bus bar lines andedge lines of the second electrode 44 in a corresponding manner. Assuch, the description given of the first-conduction-type conductiveregion 20 associated with the first electrode 42 may be applied to thesecond-conduction-type conductive region 30 associated with the secondelectrode in a corresponding manner. The description given of the firstpassivation film 22, anti-reflective film 24 and openings 102 associatedwith the first electrode 42 may be applied to the second passivationfilm 30 and openings 104 associated with the second electrode 44 in acorresponding manner.

The width, pitch, number, etc., of finger lines 44 a, the widths of lineand pad sections of bus bar lines 44 b and the pitch, number, etc., ofthe bus bar lines 44 b in the second electrode 44 may be equal to thewidth, pitch, number, etc., of finger lines 42 a, the widths of the lineand pad sections 421 and 422 of the bus bar lines 42 b and the pitch,number, etc., of the bus bar lines 42 b in the first electrode 42,respectively. Alternatively, the width, pitch, number, etc., of fingerlines 44 a, the widths of line and pad sections of bus bar lines 44 band the pitch, number, etc., of the bus bar lines 44 b in the secondelectrode 44 may differ from the width, pitch, number, etc., of fingerlines 42 a, the widths of the line and pad sections 421 and 422 of thebus bar lines 42 b and the pitch, number, etc., of the bus bar lines 42b in the first electrode 42, respectively. For example, the electrodesections of the second electrode 44, upon which a relatively smallamount of light is incident, may have a greater width than thecorresponding electrode sections of the first electrode 42 and a smallerpitch than the corresponding electrode sections of the first electrode42. Other variations are possible. Of course, the number and pitch ofthe bus bar lines 42 b in the first electrode 42 may be equal to thoseof the second electrode 44. In addition, the second electrode 44 mayhave a planar shape different from that of the first electrode 42. Othervariations are possible. For example, the length of each pad section 422disposed at the back surface of the semiconductor substrate 160 may begreater than the length of each pad section 422 disposed at the frontsurface of the semiconductor substrate 160. This is because it isdifficult for the pad section 422 disposed at the front surface of thesemiconductor substrate 160 to have a great length, taking shading lossinto consideration, whereas relatively small shading loss occurs at theback surface of the semiconductor substrate 160.

In accordance with this embodiment, it may be possible to minimizeshading loss through diffuse reflection, using the wire-shaped leads142. It may also possible to reduce the movement path of carriers byreducing the pitch of the leads 142. Accordingly, efficiency of thesolar cell 150 and output power of the solar cell panel 100 may beenhanced. In addition, it may be possible to enhance attachment forcebetween each wire-shaped lead 142 and the first electrode 42 by definingthe edge distance D of the first pad section 422 a in accordance withthe width of the lead 142. Accordingly, damage to the solar cell 150 orthe like, which may occur due to separation of the lead 142 from thefirst electrode 42, may be prevented and, as such, the solar cell 150may have superior electrical characteristics and reliability. Inaddition, it may be possible to maximize output power of the solar cellpanel 100 by defining the number of leads 142 in accordance with thewidth W1 of each lead 142.

In this embodiment, each of the electrode portions 424 a and 424 brespectively disposed at the first and second end edge areas PA3 and PA4are disposed at a position flush with corresponding ones of theoutermost finger lines 421 a and 421 b or a position outwards of thecorresponding outermost finger lines 421 a or 421 b and, as such, maystably form a connection structure to the corresponding lead 142. It maybe possible to effectively transfer current generated at portions of theelectrode areas EA respectively disposed adjacent to the first andsecond end edge areas PA3 and PA4 to the lead 142 via the electrodeportions 424 a and 424 b respectively disposed at the first and secondend edge areas PA3 and PA4. Accordingly, current generated at portionsof the electrode areas EA respectively disposed adjacent to the firstand second end edge areas PA3 and PA4 may be effectively transferred tothe lead 142 by the electrode portions 424 a and 424 b. Thus, even whenthe first edge areas PA1 (or the first and second end edge areas PA3 andPA4) are provided to achieve an enhancement in the attachment force orcoupling force of the leads 142, it may be possible to avoid anefficiency reduction that may be caused by the provision of the firstedge areas PA1. Thus, the efficiency of the solar cell 150 may beenhanced and, as such, the output power of the solar cell panel 100 maybe enhanced. Accordingly, the efficiency of the solar cell 150 may beenhanced and, as such, the output power of the solar cell panel 100 maybe enhanced.

In addition, the electrode portion 424 a disposed at the first end edgearea PA3 and the electrode portion 424 b disposed at the second end edgearea PA4 may have different shapes and, as such, it may be possible tosimplify the electrode structures of the electrode portions 424 a and424 b while stably forming the connection structures of the electrodeportions 424 a and 424 b to the lead 142.

Hereinafter, a solar cell according to another embodiment of the presentinvention and a solar cell panel including the same will be describedwith reference to the accompanying drawings. The above description maybe applied to parts identical or similar to those described above in thesame manner and, as such, no description will be given of the identicalor similar parts, and only parts different from those described abovewill be described in detail. Combinations of the above-describedembodiment, variations thereof, the following embodiment and variationsof the following embodiment also fall within the scope of the presentinvention. Although the following description is given in conjunctionwith, for example, the first electrode, the following illustration andexplanation may also be applied to the second electrode in the samemanner.

FIG. 13 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention. (a)of FIG. 13 illustrates the first end edge area PA3 of the solar cell,and (b) of FIG. 13 illustrates the second end edge area PA4 of the solarcell.

Referring to (a) of FIG. 13 , the second electrode part 4242 in thefirst end edge area PA3 protrudes farther toward the first edge 161 thanthe corresponding outermost finger lines 421 a. Accordingly, theconnection area or connection reliability of the second electrode part4242 to the corresponding lead 142 may be further increased.

Referring to (b) of FIG. 13 , the third electrode part 4243 in thesecond end edge area PA4 may protrude farther toward the second edge 162than the corresponding outermost finger lines 421 b. That is, the thirdelectrode part 4243 may have a shape protruding outwards of theoutermost finger lines 421 b while being connected to the outermostfinger lines 421 b. In this embodiment, for example, the third electrodepart 4243 is illustrated as being parallel to the outermost finger lines421 b at a central region thereof while being inclined from theoutermost finger lines 422 a at opposite ends thereof. Of course, theembodiment of the present invention is not limited to theabove-described shape, and the third electrode part 4243 may havevarious shapes.

FIG. 14 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention.

Referring to FIG. 14 , the third electrode part 4243 may have a greaterthickness than the corresponding outermost finger lines 421 b and, assuch, the outer edge of the third electrode part 4243 may have a shapeprotruding toward the second edge 162 beyond the outermost finger lines421 b. When the third electrode part 4243 has a relatively greatthickness, as described above, it may be possible to increase theconnection area of the third electrode part 4243 to the lead 142 in thesecond end edge area PA4.

FIG. 15 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention.

Referring to FIG. 15 , the third electrode part 4243 is illustrated ashaving a greater thickness than the corresponding outermost finger lines421 b while having an outer edge disposed to be flush with the outermostfinger lines 421 b and an inner edge disposed inwards of the outermostfinger lines 422 a. When the third electrode part 4243 has a relativelygreat thickness, as described above, it may be possible to increase theconnection area of the third electrode part 4243 to the lead 142 in thesecond end edge area PA4.

FIG. 16 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention.

Referring to (a) and (b) of FIG. 16 , in this embodiment, the electrodeportion 424 a disposed at the first end edge area PA3 and the electrodeportion 424 b disposed at the second end edge area PA4 may havesymmetrical shapes. For example, the electrode portion 424 a disposed atthe first end edge area PA3 and the electrode portion 424 b disposed atthe second end edge area PA4 may be symmetrical with reference to avirtual line parallel to the finger lines 42 a while passing through thecenter of the solar cell 150. Accordingly, the opening of the electrodeportion 424 a disposed at the first end edge area PA3 and the opening ofthe electrode portion 424 b disposed at the second end edge area PA4 mayalso have symmetrical shapes or arrangement.

For example, referring to (a) of FIG. 16 , the electrode portion 424 ain the first end edge area PA3 may include a first electrode part 4241disposed inwards of the corresponding outermost finger lines 421 a, anda second electrode part 4242 extending from the first electrode part4241 to a position flush with the outermost finger lines 421 a or aposition outwards of the outermost finger lines 421 a in a directioncrossing the first electrode part 4241. The shape of the electrodeportion 424 a in the first end edge area PA3 is identical or verysimilar to the shape of the electrode portion 424 a in the first endedge area PA3 described with reference to FIG. 9 and, as such, nodetailed description thereof will be given.

Meanwhile, referring to (b) of FIG. 16 , the electrode portion 424 b inthe second end edge area PA4 may include a first electrode part 4241disposed inwards of the corresponding outermost finger lines 421 b, anda second electrode part 4242 extending from the first electrode part4241 to a position flush with the outermost finger lines 421 b or aposition outwards of the outermost finger lines 421 b in a directioncrossing the first electrode part 4241. The shape of the electrodeportion 424 b in the second end edge area PA4 is identical or verysimilar to the shape of the electrode portion 424 a in the first endedge area PA3 described with reference to FIG. 9 and, as such, nodetailed description thereof will be given.

Accordingly, the first electrode part 4241 disposed at the first endedge area PA3 and the first electrode part 4241 disposed at the secondend edge area PA4 are arranged at symmetrical positions, respectively,while having the same or very similar shapes, lengths and widths. Inaddition, the second electrode part 4242 disposed at the first end edgearea PA3 and the second electrode part 4242 disposed at the second endedge area PA4 are arranged at symmetrical positions, respectively, whilehaving the same or very similar shapes, lengths and widths.

Of course, the embodiment of the present invention is not limited to theabove-described conditions. For example, although the electrode portion424 a disposed at the first end edge area PA3 and the electrode portion424 b disposed at the second end edge area PA4 are arranged atsymmetrical positions, respectively, the shapes, lengths and widthsthereof may differ from each other. Alternatively, although theelectrode portion 424 a disposed at the first end edge area PA3 and theelectrode portion 424 b disposed at the second end edge area PA4 are notarranged at accurately symmetrical positions, respectively, at least oneof the shapes, lengths and widths thereof may be the same or verysimilar. Other variations are possible.

In this embodiment, simplification of the structure and uniform flow ofcurrent may be achieved because the electrode portion 424 a disposed atthe first end edge area PA3 and the electrode portion 424 b disposed atthe second end edge area PA4 are formed to be symmetrical.

FIG. 16 illustrates each of the electrode portions 424 a and 424 bdisposed at the first and second end edge areas PA3 and PA4 as includingthe first and second electrode parts 4241 and 4242. However, theembodiment of the present invention is not limited to theabove-described structure. The electrode portions 424 a and 424 bdisposed at the first and second end edge areas PA3 and PA4 may havevarious shapes. This will be described with reference to FIG. 17 .

FIG. 17 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention.

Referring to (a) and (b) of FIG. 17 , in this embodiment, the electrodeportion 424 a disposed at the first end edge area PA3 and the electrodeportion 424 b disposed at the second end edge area PA4 may havesymmetrical shapes, as illustrated in FIG. 16 .

For example, referring to (a) of FIG. 17 , the electrode portion 424 ain the first end edge area PA3 may include a first electrode part 4241disposed inwards of the corresponding outermost finger lines 421 a, asecond electrode part 4242 extending from the first electrode part 4241to a position flush with the outermost finger lines 421 a or a positionoutwards of the outermost finger lines 421 a in a direction crossing thefirst electrode part 4241, and a third electrode part 4243 disposed at aposition flush with the outermost finger lines 421 a or a positionoutwards of the outermost finger lines 421 a. The second electrode part4242 may reach the third electrode part 4243 and, as such, may beconnected to the third electrode part 4243. In addition, the thirdelectrode part 4243 may connect the outermost finger lines 421 adisposed at opposite sides of the first end edge area PA3.

In addition, referring to (b) of FIG. 17 , the electrode portion 424 bin the second end edge area PA4 may include a first electrode part 4241disposed inwards of the corresponding outermost finger lines 421 b, asecond electrode part 4242 extending from the first electrode part 4241to a position flush with the outermost finger lines 421 b or a positionoutwards of the outermost finger lines 421 b in a direction crossing thefirst electrode part 4241, and a third electrode part 4243 disposed at aposition flush with the outermost finger lines 421 b or a positionoutwards of the outermost finger lines 421 b. The second electrode part4242 may reach the third electrode part 4243 and, as such, may beconnected to the third electrode part 4243. In addition, the thirdelectrode part 4243 may connect the outermost finger lines 421 bdisposed at opposite sides of the second end edge area PA4.

In this embodiment, openings are formed in a closed space defined by thefirst electrode part 4241, second electrode part 4242, third electrodepart 4243 and extension sections 423 in each of the first and second endedge area PA3 and PA4. For example, two openings may be provided betweenthe extension sections 423 at opposite sides of the second electrodepart 4242, respectively, and one opening may be provided among the firstelectrode part 4241 and extension sections 423.

As illustrated in FIG. 17 , the first electrode part 4241 disposed atthe first end edge area PA3 and the first electrode part 4241 disposedat the second end edge area PA4 are arranged at symmetrical positions,respectively, while having the same or very similar shapes, lengths andwidths. In addition, the second electrode part 4242 disposed at thefirst end edge area PA3 and the second electrode part 4242 disposed atthe second end edge area PA4 may be arranged at symmetrical positions,respectively, while having the same or very similar shapes, lengths andwidths. In addition, the third electrode part 4243 disposed at the firstend edge area PA3 and the third electrode part 4243 disposed at thesecond end edge area PA4 may be arranged at symmetrical positions,respectively, while having the same or very similar shapes, lengths andwidths.

Of course, the embodiment of the present invention is not limited to theabove-described arrangements. For example, although the electrodeportion 424 a disposed at the first end edge area PA3 and the electrodeportion 424 b disposed at the second end edge area PA4 are arranged atsymmetrical positions, respectively, the shapes, lengths and widthsthereof may differ from each other. Alternatively, although theelectrode portion 424 a disposed at the first end edge area PA3 and theelectrode portion 424 b disposed at the second end edge area PA4 are notarranged at accurately symmetrical positions, respectively, at least oneof the shapes, lengths and widths thereof may be the same or verysimilar. Other variations are possible.

Detailed descriptions of the first to third electrode parts 4241, 4242,and 4243 are identical or very similar to those of the first to thirdelectrode parts 4241, 4242, and 4243 given with reference to FIG. 9 and,as such, may not be given. The present invention may further include anembodiment in which the electrode portion 424 a disposed at the firstend edge area PA3 in the instance of FIG. 9 has the shape illustrated in(a) of FIG. 17 .

In this embodiment, each of the electrode portions 424 a and 424 brespectively disposed at the first and second end edge areas PA3 and PA4includes the first to third electrode parts 4241, 4242, and 4243 and, assuch, various current paths are provided. Accordingly, current may moresmoothly flow.

FIG. 18 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention.

Referring to FIG. 18 , the solar cell may include line breaking sectionsS, at which finger lines 42 a arranged between two neighboring bus barlines 42 b are broken at respective parts thereof without extendingcontinuously.

In this instance, the line breaking sections S may be formed at thefinger lines 42 a arranged in the first electrode areas EA1,respectively, and may not be formed at the finger lines 42 a arranged inthe second electrode areas EA2. Although the finger lines 42 a in eachfirst electrode area EA1 have respective line breaking sections S,current may smoothly flow through the finger lines 42 a because thefinger lines 42 a are connected to two neighboring bus bar lines 42 b orleads 142 at opposite sides thereof. In this instance, accordingly, itmay be possible to reduce the area of the first electrode 42 withoutobstructing flow of current in the first electrode area EA1 and, assuch, manufacturing costs and shading loss may be reduced. On the otherhand, the finger lines 42 a in each second electrode area EA2 areconnected to one bus bar line 42 b or lead 142 only at one side thereof,and have no line breaking section S and, as such, current may smoothlyflow to the bus bar line 42 b or lead 142 disposed at one side of thefinger lines 42 a.

The line breaking sections S of the finger lines 42 a in each firstelectrode area EA1 may be centrally arranged between two neighboring busbar lines 42 b corresponding to the first electrode area EA1.Accordingly, it may be possible to minimize a current movement path.

The width of each line breaking section S may be 0.5 times or more thepitch of each finger line 42 a, and may be 0.5 times or less the pitchof each bus bar line 42 b. When the width of each line breaking sectionS is less than 0.5 times the pitch of each finger line 42 a, effects ofthe line breaking section S may be insufficient because the linebreaking section S is too narrow. On the other hand, when the width ofeach line breaking section S is greater than 0.5 times the pitch of eachbus bar line 42 b, electrical characteristics may be degraded becausethe line breaking section S is too wide. For example, the width of theline breaking section S may be 1.5 to 3.2 mm. Meanwhile, for example,the width of each line breaking section S may be greater than the widthW6 of each pad section 422 in each bus bar line 42 b. Within this range,effects of the line breaking section S may be maximized. Of course, theembodiment of the present invention is not limited to theabove-described conditions, and the width of each line breaking sectionS may have various values.

The ratio of the number of finger lines 42 a having line breakingsections S in each first electrode area EA1 may be 0.33 to 1 times thetotal number of finger lines 42 a in the first electrode area EA1 whenthe numbers of the finger lines 42 a are measured in a directionparallel to the bus bar lines 42 b. Within this range, effects of theline breaking section S may be maximized. Of course, the embodiment ofthe present invention is not limited to the above-described conditions,and the above-described number ratio may be varied.

Although the line breaking sections S are illustrated in FIG. 18 asbeing provided at each first electrode area EA1, the embodiment of thepresent invention is not limited thereto. The line breaking sections Smay be provided at a part of the plurality of first electrode areas EA1,and may not be provided at the remaining part of the plurality of firstelectrode areas EA1. Alternatively, a plurality of line breakingsections S (for example, two or more line breaking sections S) may beprovided at each finger line 42 a. In addition, positions of the linebreaking sections S in one finger line 42 a may differ from those ofanother finger line 42 a. Although the line breaking sections S areillustrated in FIG. 18 as being provided at the first electrode areasEA1 without being provided at the second electrode areas EA2, theembodiment of the present invention is not limited thereto. For example,the line breaking sections S may be provided at both the first electrodeareas EA1 and the second electrode areas EA2. In the drawings and abovedescription, although illustration and description has been given inconjunction with the first electrode 42, the description may be appliedto the second electrode 44 in the same manner.

FIG. 19 is a plan view illustrating a portion of the front surface of asolar cell according to another embodiment of the present invention.

Referring to FIG. 19 , the solar cell may include finger lines 42 a eacharranged between two neighboring bus bar lines 42 b while havingportions having different line widths. Each of the finger lines 42 a mayinclude a narrow portion S1 having a relatively small width, and a wideportion S2 having a relatively great width.

For example, in this embodiment, each of the finger lines 42 a arrangedin each first electrode area EA1 may include a narrow portion S1 and awide portion S2, and each of the finger lines 42 a arranged in eachsecond electrode area EA2 has a uniform width (for example, a widthequal to that of the wide portion S2). In the first electrode area EA1,current may smoothly flow because the finger lines 42 a are connectedbetween two neighboring bus bar lines 42 b or leads 142. Accordingly, itmay be possible to reduce the area of the first electrode 42 by virtueof the narrow portions S1 of the first electrode 42 without obstructingflow of current and, as such, manufacturing costs and shading loss maybe reduced. On the other hand, in the second electrode area EA2, thefinger lines 42 a are connected to one bus bar line 42 b or lead 142only at one side thereof, and have a uniform width because no narrowportion S1 is provided and, as such, current may flow to the bus barline 42 b or lead 142 disposed at one side of the finger lines 42 a.

In this embodiment, the narrow portions S1 of the finger lines 42 a maybe centrally arranged between two neighboring bus bar lines 42 b, andthe finger lines 42 a may have a width gradually increasing toward thetwo neighboring bus bar lines 42 b. Accordingly, smooth current flow maybe achieved. Of course, the embodiment of the present invention is notlimited to the above-described conditions, and the finger lines 42 aeach having the narrow portion S1 and wide portion S2 may have variousshapes.

The ratio of the number of finger lines 42 a having narrow portions S1in each first electrode area EA1 may be 0.33 to 1 times the total numberof finger lines 42 a in the first electrode area EA1 when the numbers ofthe finger lines 42 a are measured in a direction parallel to the busbar lines 42 b. Within this range, effects of the line breaking sectionS may be maximized.

Although the narrow portions S1 are illustrated in FIG. 19 as beingprovided at each first electrode area EA1, the embodiment of the presentinvention is not limited thereto. The narrow portions S1 may be providedat a part of the plurality of first electrode areas EA1, and may not beprovided at the remaining part of the plurality of first electrode areasEA1. Alternatively, a plurality of narrow portions S1 (for example, twoor more narrow portions S1) may be provided at each finger line 42 a. Inaddition, positions of the narrow portions S1 in one finger line 42 amay differ from those of another finger line 42 a. Although the narrowportions S1 are illustrated in FIG. 18 as being provided at the firstelectrode areas EA1 without being provided at the second electrode areasEA2, the embodiment of the present invention is not limited thereto. Forexample, the narrow portions S1 may be provided at both the firstelectrode areas EA1 and the second electrode areas EA2. In addition, inthe above-described modified embodiments, the line breaking section Sillustrated in FIG. 18 may be provided in combination with the narrowportion S1. In the drawings and above description, although illustrationand description has been given in conjunction with the first electrode42, the description may be applied to the second electrode 44 in thesame manner.

Hereinafter, the present invention will be described in more detail withreference to an experimental example according to the present invention.The following experimental example is only illustrative for referenceand, as such, the embodiment of the present invention is not limitedthereto.

EXPERIMENTAL EXAMPLE

A lead having a circular cross-section and a width of 300 μm wasattached to a solar cell having an edge distance of 7.5 mm. Attachmentforce was then measured while pulling the lead using an experimentaldevice (for example, a tensile testing device). The measured values ofattachment force are depicted in FIG. 20 .

In FIG. 20 , the horizontal axis represents distance, and the verticalaxis represents attachment force. The horizontal axis may be dividedinto three sections. The first section, for example, a section I, is asection in which pulling of the lead is begun, and is continued beforethe lead is tightened. The second section, for example, a section II, isa section in which the lead is actually tightened by the experimentaldevice in accordance with pulling. The third section, for example, asection III, is a section in which the lead is detached from padsections. Accordingly, actual attachment force may be measured in thesecond section II.

In the first section I, no actual force is applied to the lead becausethe first section I is a small-distance section.

In the second section II, the experimental device continuously pulls thelead. Accordingly, as the distance in the second section II increases,stress applied to the lead is increased in proportion to distance. Thus,the graph in FIG. 16 depicts a gradual increase of an attachment forcetowards an apex. For example, the attachment force gradually increasesin the second section II, and then abruptly decreases after passing anapex of 2.058N.

The third section III is a section following the apex of the attachmentforce. In the third section III, stress applied to the lead is abruptlyreduced because the lead is detached from first pad sections.

It may be seen that the attachment force of the lead according to thisembodiment exhibits a superior value of 2.058N.

The features, structures, effects, etc., as described above are includedin at least one embodiment, and are not limited to a particularembodiment. In addition, although the example embodiments of the presentinvention have been disclosed for illustrative purposes, those skilledin the art will appreciate that various modifications, additions andsubstitutions are possible, without departing from the scope and spiritof the invention as disclosed in the accompanying claims.

What is claimed is:
 1. A solar cell panel comprising: a solar cellcomprising a semiconductor substrate, a conductive region formed in oron the semiconductor substrate, and an electrode connected to theconductive region; and a plurality of lead wires electrically connectedto the electrode, to connect the solar cell to another solar cell,wherein the electrode comprises: a plurality of finger electrodes formedto extend in parallel in a first direction; busbar electrodes formed toextend in a second direction crossing the first direction and eachincluding a plurality of pad sections and a line section connecting tothe plurality of pad sections in the second direction; and a firstadditional electrode formed at a first edge area between a firstoutermost pad section among the plurality of pad sections and a firstoutermost finger electrode among the plurality of finger electrodes,wherein the first additional electrode includes a first part extendingin the first direction and a second part extending in the seconddirection, wherein each of the plurality of lead wires is overlappedwith the line section and is positioned at the first edge area to beoverlapped with at least a part of the first additional electrode,wherein each of the plurality of lead wires has a width greater than awidth of the line section, wherein the plurality of the fingerelectrodes extending in the first direction within the first edge areaare cut from each other in the first direction, and the busbarelectrodes are not formed outside the first outermost pad section, andwherein a number of the plurality of pad sections is less than a numberof intersections of the plurality of finger electrodes and the busbarelectrodes.
 2. The solar cell panel according to claim 1, wherein acouple force between the first additional electrode and the plurality oflead wires in the first edge area is less than a couple force betweenthe busbar electrodes and the plurality of lead wires in areas otherthan the first edge area.
 3. The solar cell panel according to claim 1,wherein: the first edge area is disposed at a first side of each of thebusbar electrodes in the second direction, the first additionalelectrode is connected to corresponding ones of the plurality of fingerelectrodes, the corresponding ones of the plurality of finger electrodesbeing arranged in two opposite electrode areas disposed adjacent to thefirst edge area, and the electrode further comprises a second additionalelectrode formed at a second edge area between a second outermost padsection among the plurality of pad sections and a second outermostfinger electrode among the plurality of finger electrodes at a secondside of each of the busbar electrodes opposite to the first side in thesecond direction, the second additional electrode includes a third partextending in the first direction, and the third part is connected toother corresponding ones of the plurality of finger electrodes, theother corresponding ones of the plurality of finger electrodes beingarranged in two opposite electrode areas disposed adjacent to the secondedge area.
 4. The solar cell panel according to claim 1, wherein: theelectrode further comprises a second additional electrode formed at asecond edge area between a second outermost pad section among theplurality of pad sections and a second outermost finger electrode amongthe plurality of finger electrodes at a second side of each of thebusbar electrodes opposite to the first side in the second direction, anend of each of the plurality of lead wires is disposed within the firstedge area, each of the plurality of lead wires extends from the end tothe another solar cell while passing through the second edge area, andthe first additional electrode disposed at the first edge area and thesecond electrode disposed at the second edge area have different shapes,respectively.
 5. The solar cell panel according to claim 4, wherein: thefirst part is disposed inwards of the first outermost finger electrodeamong the plurality of finger electrodes, and the second part extendsfrom the first part to a position flush with the first outermost fingerelectrode or a position outward of the first outermost finger electrodein the second direction; the third part is disposed at a position flushwith the second outermost finger electrode among the plurality of fingerelectrodes or a position outward of the second outermost fingerelectrode; at least one of the plurality of lead wires is disposed atthe first and second parts in the first edge area; and the at least oneof the plurality of lead wires is disposed at a third part in the secondedge area.
 6. The solar cell panel according to claim 5, wherein: thefirst part and the third part are parallel to the plurality of fingerelectrodes; the second part perpendicularly crosses the plurality offinger electrodes; the second part is arranged to pass through a centerof the first part; the at least one of the plurality of lead wires isarranged to cross the first part such that the end of the at least oneof the plurality of lead wires is disposed on the second part; and theat least one of the plurality of lead wires crosses the third part. 7.The solar cell panel according to claim 1, wherein: the electrodefurther comprises a second additional electrode formed at a second edgearea between a second outermost pad section among the plurality of padsections and a second outermost finger electrode among the plurality offinger electrodes at a second side of each of the busbar electrodesopposite to the first side in the second direction; an end of each ofthe plurality of lead wires is disposed within the first edge area; eachof the plurality of lead wires extends from the end to the another solarcell while passing through the second edge area; and the first additionelectrode disposed at the first edge area and the second additionalelectrode disposed at the second edge area have symmetrical shapes,respectively.
 8. The solar cell panel according to claim 1, wherein: thefirst edge area comprises an inner end disposed inward of the firstoutermost finger electrode among the plurality of finger electrodes; andthe first outermost pad section of the plurality of pad sections isdisposed at the inner end.
 9. The solar cell panel according to claim 8,wherein: each of the plurality of pad sections has a width equal to orgreater than a width of each of the plurality of lead wires; and thewidth of each of the plurality of pad sections is greater than a widtheach of the plurality of finger electrodes and a width of the linesections.
 10. The solar cell panel according to claim 8, wherein each ofthe plurality of lead wires extends to the first edge area disposedoutward of the first outermost pad section among the plurality of padsections at the inner end of the first edge area.
 11. The solar cellpanel according to claim 1, wherein each of the plurality of lead wireshas different lengths at portions thereof disposed at the first edgearea and a second edge area located between a second outermost padsection among the plurality of pad sections and a second outermostfinger electrode among the plurality of finger electrodes at a side ofeach of the busbar electrodes opposite to the first edge area in thesecond direction, respectively.
 12. The solar cell panel according toclaim 1, wherein: the first edge area comprises an inner end disposedinward of the first outermost finger electrode among the plurality offinger electrodes; and when “W” represents a width of each of theplurality of lead wires, and “D” represents an edge distance between theinner end of the first edge area and a corresponding edge of thesemiconductor substrate, “W” and “D” satisfy the following Expression:13.732*In(W)−71.436−0.0000321462*(W)²≤D≤13.732*In(W)−71.436+0.0000321462*(W)²,  <Expression> where the unitof “W” is μm, and the unit of “D” is mm.
 13. The solar cell panelaccording to claim 12, wherein: the width of each of the plurality oflead wires is 250 to 500 μm; the edge distance is 2.37 to 21.94 mm; andthe plurality of lead wires comprises 6 to 33 leads arranged withreference to one surface of the solar cell.
 14. The solar cell panelaccording to claim 1, wherein: the first additional electrode has awidth equal to or greater than a width of each of the plurality offinger electrodes, and is smaller than a pitch between adjacent pairs ofthe plurality of finger electrodes; each of the plurality of lead wireshas a greater width than the width of the first additional electrode;and the first outermost finger electrode comprises two first outermostfinger electrodes arranged in two opposite electrode areas disposedadjacent to the first edge area, and the first edge area has a greaterwidth between the two first outermost finger electrodes among theplurality of finger electrodes than the width of one of the plurality oflead wires.
 15. The solar cell panel according to claim 1, wherein thefirst edge area has a shape having a width gradually increasing towardsa corresponding edge of the semiconductor substrate.
 16. The solar cellpanel according to claim 1, further comprising: extension sections eacharranged between the first edge area and an electrode area disposedadjacent to the first edge area, to divide the first edge area from theelectrode area; two or more of the plurality of finger electrodes areconnected to each of the extension sections; and the first additionalelectrode in the first edge area is connected to corresponding ones ofthe plurality of finger electrodes via the extension sections.
 17. Thesolar cell panel according to claim 1, wherein a width of the first edgearea is smaller than a length of the first edge area between the firstoutermost pad section and the first outermost finger electrode.
 18. Thesolar cell panel according to claim 1, wherein the second part isconnected to the first part and spaced apart from the busbar electrodeswithout directly contacting the busbar electrodes.
 19. The solar cellpanel according to claim 1, wherein a length of the first edge areabetween the first outermost pad section and the first outermost fingerelectrode is larger than a length of a portion of each lead wiredisposed at the first edge area among the plurality of lead wires.